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Philosophy of Mind |
The branch of philosophy that includes the philosophy of psychology, philosophical psychology, and the area of metaphysics concerned with the nature of mental phenomena and how they fit into the causal structure of reality. Philosophy of psychology, a branch of the philosophy of science, examines what psychology says about the nature of psychological phenomena; examines aspects of psychological theorizing such as the models used, explanations offered, and laws invoked; and examines how psychology fits with the social sciences and natural sciences. Philosophical psychology investigates folk psychology, a body of commonsensical, protoscientific views about mental phenomena. Such investigations attempt to articulate and refine views found in folk psychology about conceptualization, memory, perception, sensation, consciousness, belief, desire, intention, reasoning, action, and so on. The mind-body problem, a central metaphysical one in the philosophy of mind, is the problem of whether mental phenomena are physical and, if not, how they are related to physical phenomena. Other metaphysical problems in the philosophy of mind include the free will problem, the problem of personal identity, and the problem of how, if at all, irrational phenomena such as akrasia and self-deception are possible.
The doctrine that the soul is distinct from the body is found in Plato and discussed throughout the history of philosophy, but Descartes is considered the father of the modern mind—body problem. He maintained that the essence of the physical is extension in space. Minds are unextended substances and thus are distinct from any physical substances. The essence of a mental substance is to think. This twofold view is called Cartesian dualism. Descartes was well aware of an intimate relationship between mind and the brain. (There is no a priori reason to think that the mind is intimately related to the brain; Aristotle, e.g., did not associate them.) Descartes (mistakenly) thought the seat of the relationship was in the pineal gland. He maintained, however, that our minds are not our brains, lack spatial location, and can continue to exist after the death and destruction of our bodies. Cartesian dualism invites the question: What connects the mind and brain? Causation is Descartes’s answer: states of our minds causally interact with states of our brains. When bodily sensations such as aches, pains, itches, and tickles cause us to moan, wince, scratch, or laugh, they do so by causing brain states (events, processes), which in turn cause bodily movements. In deliberate action, we act on our desires, motives, and intentions to carry out our purposes; and acting on these mental states involves their causing brain states, which in turn cause our bodies to move, thereby causally influencing the physical world. The physical world, in turn, influences our minds through its influence on our brains. Perception of the physical world with five senses—sight, hearing, smell, taste, and touch—involves causal transactions from the physical to the mental: what we perceive (i.e., see, hear, etc.) causes a sense experience (i.e., a visual experience, aural experience, etc.). Thus, Descartes held that there is two-way psychophysical causal interaction: from the mental to the physical (as in action) and from the physical to the mental (as in perception). The conjunction of Cartesian dualism and the doctrine of two-way psychophysical causal interaction is called Cartesian interactionism. Perhaps the most widely discussed difficulty for this view is how states of a non-spatial substance (a mind) can causally interact with states of a substance that is in space (a brain). Such interactions have seemed utterly mysterious to many philosophers. Mystery would remain even if an unextended mind is locatable at a point in space (say, the center of the pineal gland). For Cartesian interactionism would still have to maintain that causal transactions between mental states and brain states are fundamental, i.e., unmediated by any underlying mechanism. Brain states casually interact with mental states, but there is no answer to the question of how they do so. The interactions are brute facts. Many philosophers, including many of Descartes’s contemporaries, have found that difficult to accept.
Malebranche and Leibniz, among others, rejected the possibility of psychophysical causal interaction. They espoused versions of parallelism: the view that the mental and physical realms run in parallel, in that types of mental phenomena co-occur with certain types of physical phenomena, but these co-occurrences never involve causal interactions. On all extant versions, the parallels hold because of God’s creation. Leibniz’s parallelism is preestablished harmony: the explanation of why mental types and certain physical types co-occur is that in the possible world God actualized (i.e., this world) they co-occur. In discussing the relation between the mental and physical realms, Leibniz used the analogy of two synchronized but unconnected clocks. The analogy is, however, somewhat misleading; suggesting causal mechanisms internal to each clock and intramental and intraphysical (causal) transactions. But Leibniz’s monadology doctrine excludes the possibility of such transactions: mental and physical phenomena have no effects even within their own realms. Malebranche is associated with occasionalism, according to which only God, through his continuous activities, causes things to happen: non-divine phenomena never cause anything. Occasionalism differs from preestablished harmony in holding that God is continually engaged in acts of creation; each moment creating the world anew, in such a way that the correlations hold. Both brands of parallelism face formidable difficulties. First, both rest on highly contentious, obscure theological hypotheses. The contention that God exists and the creation stories in question require extensive defense and explanation. God’s relationship to the world can seem at least as mysterious as the relationship Descartes posits between minds and brains. Second, since parallelism denies the possibility of psychophysical interaction, its proponents must offer alternatives to the causal theory of perception and the causal theory of action or else deny that we can perceive and that we can act intentionally. Third, since parallelism rejects intramental causation, it must either deny that reasoning is possible or explain how it is possible without causal connections between thoughts. Fourth, since parallelism rejects physical transactions, it is hard to see how it can allow, e.g., that one physical thing ever moves another; for that would require causing a change in location. Perhaps none of these weighty difficulties is ultimately insuperable; in any case, parallelism has been abandoned.
Empirical research gives every indication that the occurrence of any brain state can, in principle, be causally explained by appeal solely to other physical states. To accommodate this, some philosophers espoused epiphenomenalism, the doctrine that physical states cause mental states, but mental states do not cause anything. (This thesis was discussed under the name ‘conscious automatism’ by Huxley and Hogeson in the late nineteenth century. William James was the first to use the term ‘epiphenomena’ to mean phenomena that lack causal efficacy. And James Ward coined the term ‘epiphenomenalism’ in 1903.) Epiphenomenalism implies that there is only one-way psychophysical action—from the physical to the mental. Since epiphenomenalism allows such causal action, it can embrace the causal theory of perception. However, when combined with Cartesian dualism, epiphenomenalism, like Cartesian interactionism, implies the problematic thesis that states of an extended substance can affect states of an unextended substance. An epiphenomenalist can avoid this problem by rejecting the view that the mind is an unextended substance while maintaining that mental states and events are nonetheless distinct from physical states and events. Still, formidable problems would remain. It is hard to see how epiphenomenalism can allow that we are ever intentional agents. For intentional agency requires acting on reasons, which, according to the causal theory of action, requires a causal connection between reasons and actions. Since epiphenomenalism denies that such causal connections are possible, it must either maintain that our sense of agency is illusory or offer an alternative to the causal theory of action. Similarly, it must explain how thinking is possible given that there are no causal connections between thoughts.
Many philosophers reject Descartes’s bifurcation of reality into mental and physical substances. Spinoza held a dualattribute theory—also called the dual-aspect theory—according to which the mental and the physical are distinct modes of a single substance, God. The mental and the physical are only two of infinitely many modes of this one substance. Many philosophers opted for a thoroughgoing monism, according to which all of reality is really of one kind. Materialism, idealism, and neutral monism are three brands of monism. Hobbes, a contemporary of Descartes, espoused materialism, the brand of monism according to which everything is material or physical. Berkeley is associated with idealism, the brand of monism according to which everything is mental. He held that both mental and physical phenomena are perceptions in the mind of God. For Hegel’s idealism, everything is part of the World Spirit. The early twentieth-century British philosophers Bradley and McTaggart also held a version of idealism. Neutral monism is the doctrine that all of reality is ultimately of one kind, which is neither mental nor physical. Hume was a neutral monist, maintaining that mental and physical substances are really just bundles of the neutral entities. Versions of neutral monism were later held by Mach and, for a short time, Russell. Russell called his neutral entities sensibilia and claimed that minds and physical objects are logical constructions out of them.
This view, espoused in the twentieth century by, among others, Ayer, argues that all empirical statements are synonymous with statements solely about phenomenal appearances. While the doctrine is about statements, phenomenalism is either a neutral monism or an idealism, depending on whether phenomenal appearances are claimed to be neither mental nor physical or, instead, mental. The required translations of physical statements into phenomenal ones proved not to be forthcoming, however. Chisholm offered a reason why they would not be: what appearances a physical state of affairs (e.g., objects arrayed in a room) has depends both on physical conditions of observation (e.g., lighting) and physical conditions of the perceiver (e.g., of the nervous system). At best, a statement solely about phenomenal appearances is equivalent to one about a physical state of affairs, only when certain physical conditions of observation and certain physical conditions of the perceiver obtain.
Two problems face any monism: it must characterize the phenomena it takes as basic, and it must explain how the fundamental phenomena make up non-basic phenomena. The idealist and neutral monist theories proposed thus far have faltered on one or both counts. Largely because of scientific successes of the twentieth century, such as the rebirth of the atomic theory of matter, and the successes of quantum mechanics in explaining chemistry and of chemistry in turn in explaining much of biology, many philosophers today hold that materialism will ultimately succed where idealism and neutral monism apparently failed. Materialism, however, comes in many different varieties and each faces formidable difficulties.
Ryle ridiculed Cartesianism as the view that there is a ghost in the machine (the body). He claimed that the view that the mind is a substance rests on a category mistake: ‘mind’ is a noun, but does not name an object. Cartesianism confuses the logic of discourse about minds with the logic of discourse about bodies. To have a mind is not to possess a special sort of entity; it is simply to have certain capacities and dispositions. (Compare the thesis that to be alive is to possess not a certain entity, an entelechy or élan vital, but rather certain capacities and dispositions.) Ryle maintained, moreover, that it was a mistake to regard mental states such as belief, desire, and intention as internal causes of behavior. These states, he claimed, are dispositions to behave in overt ways. In part in response to the dualist point that one can understand our ordinary psychological vocabulary (‘belief’, ‘desire’, ‘pain’, etc.) and know nothing about the physical states and events in the brain, logical behaviorism has been proposed as a materialist doctrine that explains this fact. On this view, talk of mental phenomena is shorthand for talk of actual and potential overt bodily behavior (i.e., dispositions to overt bodily behavior). Logical behaviorism was much discussed from roughly the 1930s until the early 1960s. (While Ryle is sometimes counted as a logical behaviorist, he was not committed to the thesis that all mental talk can be translated into behavioral talk.) The translations promised by logical behaviorism appear unachievable. As Putnam and others pointed out, one can fake being in pain and one can be in pain and yet not behave or be disposed to behave as if one were in pain (e.g., one might be paralyzed or might be a “super-spartan”). Logical behaviorism faces similar difficulties in translating sentences about (what Russell called) propositional attitudes (i.e., beliefs that p, desires that p, hopes that p, intentions that p, and the like). Consider the following sample proposal (similar to one offered by Carnap): one believes that the cat is on the mat if and only if one is disposed to assent to ‘The cat is on the mat’. First, the proposed translation meets the condition of being purely behavioral only if assenting is understandable in purely behavioral terms. That is doubtful. The proposal also fails to provide a sufficient or a necessary condition: someone may assent to ‘The cat is on the mat’ and yet not believe the cat is on the mat (for the person may be trying to deceive); and a belief that the cat is on the mat will dispose one to assent to ‘The cat is on the mat’ only if one understands what is being asked, wants to indicate that one believes the cat is on the mat, and so on. But none of these conditions is required for believing that the cat is on the mat. Moreover, to invoke any of these mentalistic conditions defeats the attempt to provide a purely behavioral translation of the belief sentence. Although the project of translation has been abandoned, in recent years Dennett has defended a view in the spirit of logical behaviorism, intentional systems theory: belief-desire talk functions to characterize overall patterns of dispositions to overt behavior (in an environmental context) for the purposes of predicting overt behavior. The theory is sometimes characterized as supervenient behaviorism since it implies that whether an individual has beliefs, desires, intentions and the like supervenes on his dispositions to overt behavior: if two individuals are exactly alike in respect of their dispositions to overt behavior, the one has intentional states if and only if the other does. (This view allows, however, that the contents of an individual’s intentional states—what the individual believes, desires, etc.—may depend on environmental factors. So it is not committed to the supervemence of the contents of intentional states on dispositions to overt behavior. See the discussion of content externalism below.) One objection to this view, due to Ned Block, is that it would mistakenly count as an intentional agent a giant look-up table—“a Blockhead”—that has the same dispositions to peripheral behavior as a genuine intentional agent. (A look-up table is a simple mechanical device that looks up preprogrammed responses.)
In the early 1950s, Herbert Feigl claimed that mental states are brain states. He pointed out that if mental properties or state types are merely nomologically correlated with physical properties or state types, the connecting laws would be “nomological danglers”: irreducible to physical laws, and thus additional fundamental laws. According to the identity theory, the connecting laws are not fundamental laws (and so not nomological danglers) since they can be explained by identifying the mental and physical properties in question. In the late 1950s and the early 1960s, the philosopher Smart and the psychologist U.T. Place defended the materialist view that sensations are identical with brain processes. Smart claimed that while mental terms differ in meaning from physical terms, scientific investigation reveals that they have the same referents as certain physical terms. (Compare the fact that while ‘the Morning Star’ and ‘the Evening Star’ differ in meaning empirical investigation reveals the same referent: Venus.) Smart and Place claimed that feeling pain, e.g., is some brain process, exactly which one to be determined by scientific investigation. Smart claimed that sensation talk is paraphraseable in topic-neutral terms; i.e., in terms that leave open whether sensational properties are mental or physical. ‘I have an orange afterimage’ is paraphraseable (roughly) as: ‘There is something going on like what is going on when I have my eyes open, am awake, and there is an orange illuminated in good light in front of me, i.e., when I really see an orange’. The description is topic-neutral since it leaves open whether what is going on is mental or physical. Smart maintained that scientific investigation reveals that what in fact meets the topic-neutral description is a brain process. He held that psychophysical identity statements such as ‘Pain is C-fiber firing’ are contingent, likening these to, e.g., ‘Lightning is electrical discharge’, which is contingent and knowable only through empirical investigation.
This brand of materialism was defended in the late 1960s and the early 1970s by Armstrong and others. On this view, mental states are states that are apt to produce a certain range of behavior. Central state materialists maintain that scientific investigation reveals that such states are states of the central nervous system, and thus that mental states are contingently identical with states of the central nervous system. Unlike logical behaviorism, central state materialism does not imply that mental sentences can be translated into physical sentences. Unlike both logical behaviorism and intentional systems theory, central state materialism implies that mental states are actual internal states with causal effects. And unlike Cartesian interactionism, it holds that psychophysical interaction is just physical causal interaction. Some central state materialists held in addition that the mind is the brain. However, if the mind were the brain, every change in the brain would be a change in the mind; and that seems false: not every little brain change amounts to a change of mind. Indeed, the mind ceases to exist when brain death occurs, while the brain continues to exist. The moral that most materialists nowadays draw from such considerations is that the mind is not any physical substance, since it is not a substance of any sort. To have a mind is not to possess a special substance, but rather to have certain capacities—to think, feel, etc. To that extent, Ryle was right. However, central state materialists insist that the properly functioning brain is the material seat of mental capacities, that the exercise of mental capacities consists of brain processes, and that mental states are brain states that can produce behavior. Epistemological objections have been raised to identity theories. As self-conscious beings, we have a kind of privileged access to our own mental states. The exact avenue of privileged access, whether it is introspection or not, is controversial. But it has seemed to many philosophers that our access to our own mental states is privileged in being open only to us, whereas we lack any privileged access to the states of our central nervous systems. We come to know about central nervous system states in the same way we come to know about the central nervous system states of others. So, against central state materialism and the identity theory, it is claimed that mental states cannot be states of our central nervous systems. Taking privileged access to imply that we have incorrigible knowledge of our conscious mental states, and despairing of squaring privileged access so understood with materialism, Rorty advocated eliminative materialism, the thesis that there actually are no mental phenomena. A more common materialist response, however, is to deny that privileged access entails incorrigibility and to maintain that privileged access is compatible with materialism. Some materialists maintain that while certain types of mental states (e.g., sensations) are types of neurological states, it will be knowable only by empirical investigation that they are. Suppose pain is a neural state N. It will be only a posteriori knowable that pain is N. Via the avenue of privileged access, one comes to believe that one is in a pain state, but not that one is in an N-state. One can believe one is in a pain state without believing that one is in an N-state because the concept of pain is different from the concept of N. Nevertheless, pain is N. (Compare the fact that while water is H2O, the concept of water is different from that of H2O. Thus, while water is H2O, one can believe there is water in the glass without believing that there is H2O in it. The avenue of privileged access presents N conceptualized as pain, but never as neurological state N. The avenue of privileged access involves the exercise of mental, but not neurophysiological, concepts. However, our mental concepts answer to—apply in virtue of—the same properties (state types) as do certain of our neurophysiological concepts. The identity theory and central state materialism both hold that there are contingent psychophysical property and type identities. Some theorists in this tradition tried to distinguish a notion of theoretical identity from the notion of strict identity. They held that mental states are theoretically, but not strictly, identical with brain states. Against any such distinction, Kripke argued that identities are metaphysically necessary, i.e., hold in every possible world. If A = B, then necessarily A = B. Kripke acknowledged that there can be contingent statements of identity. But such statements, he argued, will employ at least one term that is not a rigid designator, i.e., a term that designates the same thing in every world in which it designates anything. Thus, since ‘the inventor of bifocals’ is a non-rigid designator, ‘Benjamin Franklin is the inventor of bifocals’ is contingent. While Franklin is the inventor of bifocals, he might not have been. However, statements of identity in which the identity sign is flanked by rigid designators are, if true, metaphysically necessary. Kripke held that proper names are rigid designators, and hence, the true identity statement ‘Cicero is Tully’ is metaphysically necessary. Nonetheless, a metaphysically necessary identity statement can be knowable only a posteriori. Indeed, ‘Cicero is Tully’ is knowable only a posteriori. Both ‘water’ and ‘H2O’, he maintained, are rigid designators: each designates the same kind of stuff in every possible world. And he thus maintained that it is metaphysically necessary that water is H2O, despite its not being a priori knowable that water is H2O. On Kripke’s view, any psychophysical identity statement that employs mental terms and physical terms that are rigid designators will also be metaphysically necessary, if true. Central state materialists maintain that mental concepts are equivalent to concepts whose descriptive content is the state that is apt to produce such-and-such behavior in such-and-such circumstances. These defining descriptions for mental concepts are intended to be meaning-giving, not contingent reference-fixing descriptions; they are, moreover, not rigid designators. Thus, the central state materialists can concede that all identities are necessary, but maintain that psychophysical claims of identity are contingent claims of identity since the mental terms that figure in those statements are not rigid designators. However, Kripke maintained that our concepts of sensations and other qualitative states are not equivalent to the sorts of descriptions in question. The term ‘pain’, he maintained, is a rigid designator. This position might be refuted by a successful functional analysis of the concept of pain in physical and/or topic-neutral terms. However, no successful analysis of this sort has yet been produced. (See the section on consciousness below.) A materialist can grant Kripke that ‘pain’ is a rigid designator and claim that a statement such as ‘Pain is C-fiber firing’ will be metaphysically necessary if true, but only a posteriori knowable. However, Kripke raised a formidable problem for this materialism. He pointed out that if a statement is metaphysically necessary but only a posteriori knowable, its appearance of contingency calls for explanation. Despite being metaphysically necessary, ‘Water is H2O’ appears contingent. According to Kripke, we explain this appearance by noting that one can coherently imagine a world in which something has all the phenomenal properties of water, and so is an “epistemic counterpart” of it, yet is not H2O. The fact that we can coherently imagine such epistemic counterparts explains why ‘Water is H2O’ appears contingent. But no such explanation is available for (e.g.) ‘Pain is C-fiber firing’. For an epistemic counterpart of pain, something with the phenomenal properties of pain—the feel of pain—is pain. Something can look, smell, taste, and feel like water yet not be water. But whatever feels like pain is pain: pain is a feeling. In contrast, we can explain the apparent contingency of claims like ‘Water is H2O’ because water is not constituted by its phenomenal properties; our concept of water allows that it may have a “hidden essence,” i.e., an essential microstructure. If Kripke is right, then anyone who maintains that a statement of identity concerning a type of bodily sensation and a type of physical state is metaphysically necessary yet a posteriori, must explain the appearance of contingency in a way that differs from the way Kripke explains the appearance of contingency of ‘Water is H2O’. This is a formidable challenge. (The final section, on consciousness, sketches some materialist responses to it.) The general issue of property and state type identity is controversial. The claim that water is H2O despite the fact that the concept of water is distinct from the concept of H2O seems plausible. However, property or state type identity is more controversial than the identity of types of substances. For properties or state types, there are no generally accepted “non-duplication principles” —to use a phrase of David Lewis’s. (A non-duplication principle for A’s will say that no two A’s can be exactly alike in a certain respect; e.g., no two sets can have exactly the same members.) It is widely denied, for instance, that no two properties can be possessed by exactly the same things. Two properties, it is claimed, can be possessed by the same things; likewise, two state types can occur in the same space-time regions. Even assuming that mental concepts are distinct from physical concepts, the issue of whether mental state types are physical state types raises the controversial issue of the non-duplication principle for state types.
Token physicalism is the thesis that every particular is physical. Type physicalism is the thesis that every type or kind of entity is physical; thus, the identity thesis and central state materialism are type physicalist theses since they imply that types of mental states are types of physical states. Type physicalism implies token physicalism: given the former, every token falls under some physical type, and therefore is token-token identical with some token of a physical type. But token physicalism does not imply type physicalism; the former leaves open whether physical tokens fall under non-physical types. Some doctrines billed as materialist or physicalist embrace token epiphenomenalism, but reject type physicalism.
This form of materialism implies token physicalism, but denies type physicalism and, as well, that mental types (properties, etc.) are reducible to physical types. This doctrine has been discussed since at least the late nineteenth century and was widely discussed in the first third of the twentieth century. The British philosophers George Henry Lewes, Samuel Alexander, Lloyd Morgan, and C.D. Broad all held or thought plausible a certain version of non-reductive materialism. They held or sympathized with the view that every substance either is or is wholly made up of physical particles, that the well-functioning brain is the material seat of mental capacities, and that token mental states (events, processes, etc.) are token neurophysiological states (events, processes, etc.). However, they either held or thought plausible the view that mental capacities, properties, etc., emerge from, and thus do not reduce to, physical capacities, properties, etc. Lewes coined the term ‘emergence’; and Broad later labeled the doctrine emergent materialism. Emergent materialists maintain that laws correlating mental and physical properties are irreducible. (These laws would be what Feigl called nomological danglers.) Emergentists maintain that, despite their untidiness, such laws must be accepted with natural piety. Davidson’s doctrine of anomalous monism is a current brand of non-reductive materialism. He explicitly formulates this materialist thesis for events; and his irreducibility thesis is restricted to intentional mental types—e.g., believings, desirings, and intendings. Anomalous monism says that every event token is physical, but that intentional mental predicates and concepts (ones expressing propositional attitudes) do not reduce, by law or definition, to physical predicates or concepts. Davidson offers an original argument for this irreducibility thesis. Mental predicates and concepts are, he claims, governed by constitutive principles of rationality, but physical predicates and concepts are not. This difference, he contends, excludes the possibility of reduction of mental predicates and concepts to physical ones. Davidson denies, moreover, that there are strict psychological or psychophysical laws. He calls the conjunction of this thesis and his irreducibility thesis the principle of the anomalism of the mental. His argument for token physicalism (for events) appeals to the principle of the anomalism of the mental and to the principle of the nomological character of causality: when two events are causally related, they are subsumed by a strict law. He maintains that all strict laws are physical. Given that claim, and given the principle of the nomological character of causality, it follows that every event that is a cause or effect is a physical event. On this view, psychophysical causation is just causation between physical events. Stephen Schiffer has also maintained a non-reductive materialism, one he calls ontological physicalism and sentential dualism: every particular is physical, but mental truths are irreducible to physical truths. Non-reductive materialism presupposes that mental state (event) tokens can fall under physical state types and, thereby, count as physical state tokens. This presupposition is controversial; no uncontroversial non-duplication principle for state tokens settles the issue. Suppose, however, that mental state tokens are physical state tokens, despite mental state types not being physical state types. The issue of how mental state types and physical state types are related remains. Suppose that some physical token x is of a mental type M (say, a belief that the cat is on the mat) and some other physical token y is not of type M. There must, it seems, be some difference between x and y in virtue of which x is, and y is not, of type M. Otherwise, it is simply a brute fact that x is and y is not of type M. That, however, seems implausible. The claim that certain physical state tokens fall under mental state types simply as a matter of brute fact would leave the difference in question utterly mysterious. But if it is not a brute fact, then there is some explanation of why a certain physical state is a mental state of a certain sort. The non-reductive materialist owes us an explanation that does not imply psychophysical reduction. Moreover, even though the non-reductive materialist can claim that mental states are causes because they are physical states with physical effects, there is some question whether mental state types are relevant to causal relations. Suppose every state is a physical state. Given that physical states causally interact in virtue of falling under physical types, it follows that whenever states causally interact they do so in virtue of falling under physical types. That raises the issue of whether states are ever causes in virtue of falling under mental types. Type epiphenomenalism is the thesis that no state can cause anything in virtue of falling under a mental type. Token epiphenomenalism, the thesis that no mental state can cause anything, implies type epiphenomenalism, but not conversely. Non-reductive materialists are not committed to token physicalism. However, token epiphenomenalism may be false but type epiphenomenalism true since mental states may be causes only in virtue of falling under physical types, never in virtue of falling under mental types. Broad raised the issue of type epiphenomenalism and discussed whether emergent materialism is committed to it. Ted Honderich, Jaegwon Kim, Ernest Sosa, and others have in recent years raised the issue of whether non-reductive materialism is committed to type epiphenomenalism. Brian McLaughlin has argued that the claim that an event acts as a cause in virtue of falling under a certain physical type is consistent with the claim that it also acts as a cause in virtue of falling under a certain mental type, even when the mental type is not identical with the physical type. But even if this is so, the relationship between mental types and physical types must be addressed. Ernest LePore and Barry Loewer, Frank Jackson and Philip Pettit, Stephen Yablo, and others have attempted to characterize a relation between mental types and physical types that allows for the causal relevance of mental types. But whether there is a relation between mental and physical properties that is both adequate to secure the causal relevance of mental properties and available to non-reductive materialists remains an open question. Davidson’s anomalous monism may appear to be a kind of dual-aspect theory: there are events and they can have two sorts of autonomous aspects, mental and physical. However, while Davidson holds that mental properties (or types) do not reduce to physical ones, he also holds that the mental properties of an event depend on its physical properties in that the former supervene on the latter in this sense: no two events can be exactly alike in every physical respect and yet differ in some mental respect. This proposal introduced the notion of supervenience into contem- porary philosophy of mind. Often non-reductive materialists argue that mental properties (types) supervene on physical properties (types). Kim, however, has distinguished various supervenience relations, and argues that some are too weak to count as versions of materialism (as opposed to, say, dual-aspect theory), while other supervenience relations are too strong to use to formulate non-reductive materialism since they imply reducibility. According to Kim, non-reductive materialism is an unstable position.
Several philosophers have in recent years attempted to define the thesis of materialism using a global supervenience thesis. Their aim is not to formulate a brand of non-reductive materialism; they maintain that their supervenience thesis may well imply reducibility. Their aim is, rather, to formulate a thesis to which anyone who counts as a genuine materialist must subscribe. David Lewis has maintained that materialism is true if and only if any non-alien possible worlds that are physically indiscernible are mentally indiscernible as well. Non-alien possible worlds are worlds that have exactly the same perfectly natural properties as the actual world. Frank Jackson has offered this proposal: materialism is true if and only if any minimal physical duplicate of the actual world is a duplicate simpliciter of the actual world. A world is a physical duplicate of the actual world if and only if it is exactly like the actual world in every physical respect (physical particular for physical particular, physical property for physical property, physical relation for physical relation, etc.); and a world is a duplicate simpliciter of the actual world if and only if it is exactly like the actual world in every respect. A minimal physical duplicate of the actual world is a physical duplicate that contains nothing else (by way of particulars, kinds, properties, etc.) than it must in order to be a physical duplicate of the actual world. Two questions arise for any formulation of the thesis of materialism. Is it adequate to materialism? And, if it is, is it true?
The nineteenth-century British philosopher George Henry Lewes maintained that while not every neurological event is mental, every mental event is neurological. He claimed that what makes certain neurological events mental events is their causal role in the organism. This is a very early version of functionalism, nowadays a leading approach to the mind—body problem. Functionalism implies an answer to the question of what makes a state token a mental state of a certain kind M: namely, that it is an instance of some functional state type identical with M. There are two versions of this proposal. On one, a mental state type M of a system will be identical with the state type that plays a certain causal role R in the system. The description ‘the state type that plays R in the system’ will be a nonrigid designator; moreover, different state types may play R in different organisms, in which case the mental state is multiply realizable. On the second version, a mental state type M is identical with a second-order state type, the state of being in some first-order state that plays causal role R. More than one first-order state may play role R, and thus M may be multiply realizable. On either version, if the relevant causal roles are specifiable in physical or topic-neutral terms, then the functional definitions of mental state types will be, in principle, physically reductive. Since the roles would be specified partly in topic-neutral terms, there may well be possible worlds in which the mental states are realized by non-physical states; thus, functionalism does not imply token physicalism. However, functionalists typically maintain that, on the empirical evidence, mental states are realized (in our world) only by physical states. Functionalism comes in many varieties. Smart’s topic-neutral analysis of our talk of sensations is in the spirit of functionalism. And Armstrong’s central state materialism counts as a kind of functionalism since it maintains that mental states are states apt to produce a certain range of behavior, and thus identifies states as mental states by their performing this causal role. However, functionalists today typically hold that the defining causal roles include causal roles vis-à-vis input state types, as well as output state types, and also vis-à-vis other internal state types of the system in question. In the 1960s David Lewis proposed a functionalist theory, analytical functionalism, according to which definitions of mental predicates such as ‘belief’, ‘desire’, and the like (though not predicates such as ‘believes that p’ or ‘desires that q’) can be obtained by conjoining the platitudes of commonsense psychology and formulating the Ramsey sentence for the conjunction. The relevant Ramsey sentence is a second-order quantificational sentence that quantifies over the mental predicates in the conjunction of commonsense psychological platitudes, and from it one can derive definitions of the mental predicates. On this view, it will be analytic that a certain mental state (e.g., belief) is the state that plays a certain causal role vis-à-vis other states; and it is a matter of empirical investigation what state plays the role. Lewis claimed that such investigation reveals that the state types that play the roles in question are physical states. In the early 1960s, Putnam proposed a version of scientific functionalism, machine state functionalism: according to this view, mental states are types of Turing machine table states. Turing machines are mechanical devices consisting of a tape with squares on it that either are blank or contain symbols, and an executive that can move one square to the left, or one square to the right, or stay where it is. And it can either write a symbol on a square, erase a symbol on a square, or leave the square as it is. (According to the Church-Turing thesis, every computable function can be computed by a Turing machine.) Now there are two functions specifying such a machine: one from input states to output states, the other from input states to input states. And these functions are expressible by counterfactuals (e.g., ‘If the machine is in state s1 and receives input I, it will emit output O and enter state s2’). Machine tables are specified by the counterfactuals that express the functions in question. So the main idea of machine state functionalism is that any given mental type is definable as the state type that participates in certain counterfactual relationships specified in terms of purely formal, and so not semantically interpreted, state types. Any system whose inputs, outputs, and internal states are counterfactually related in the way characterized by a machine table is a realization of that table. This version of machine state functionalism has been abandoned: no one maintains that the mind has the architecture of a Turing machine. However, computational psychology, a branch of cognitive psychology, presupposes a scientific functionalist view of cognitive states: it takes the mind to have a computational architecture. (See the section on cognitive psychology below.) Functionalism—the view that what makes a state a realization of a mental state is its playing a certain causal role—remains a leading theory of mind. But functionalism faces formidable difficulties. Block has pinpointed one. On the one hand, if the input and output states that figure in the causal role alleged to define a certain mental state are specified in insufficient detail, the functional definition will be too liberal: it will mistakenly classify certain states as of that mental type. On the other hand, if the input and output states are specified in too much detail, the functional definition will be chauvinistic: it will fail to count certain states as instances of the mental state that are in fact such instances. Moreover, it has also been argued that functionalism cannot capture conscious states since types of conscious states do not admit of functional definitions.
Many claim that one aim of cognitive psychology is to provide explanations of intentional capacities, capacities to be in intentional states (e.g., believing) and to engage in intentional activities (e.g., reasoning). Fodor has argued that classical cognitive psychology postulates a cognitive architecture that includes a language of thought: a system of mental representation with a combinatorial syntax and semantics, and computational processes defined over these mental representations in virtue of their syntactic structures. On this view, cognition is rule-governed symbol manipulation. Mental symbols have meanings, but they participate in computational processes solely in virtue of their syntactic or formal properties. The mind is, so to speak, a syntactic engine. The view implies a kind of content parallelism: syntax-sensitive causal transitions between symbols will preserve semantic coherence. Fodor has maintained that, on this language-of-thought view of cognition (the classical view), being in a beliefthat-p state can be understood as consisting in bearing a computational relation (one that is constitutive of belief) to a sentence in the language of thought that means that p; and similarly for desire, intention, and the like. The explanation of intentional capacities will be provided by a computational theory for mental sentences in conjunction with a psychosemantic theory, a theory of meaning for mental sentences. A research program in cognitive science called connectionism postulates networks of neuron-like units. The units can be either on or off, or can have continuous levels of activation. Units are connected, the connections have various degrees of strength, and the connections can be either inhibitory or excitatory. Connectionism has provided fruitful models for studying how neural networks compute information. Moreover, connectionists have had much success in modeling pattern recognition tasks (e.g., facial recognition) and tasks consisting of learning categories from examples. Some connectionists maintain that connectionism will yield an alternative to the classical language-of-thought account of intentional states and capacities. However, some favor a mixed-models approach to cognition: some cognitive capacities are symbolic, some connectionist. And some hold that connectionism will yield an implementational architecture for a symbolic cognitive architecture, one that will help explain how a symbolic cognitive architecture is realized in the nervous system.
Many today hold that Twin-Earth thought experiments by Putnam and Tyler Burge show that the contents of a subject’s mental states do not supervene on intrinsic properties of the subject: two individuals can be exactly alike in every intrinsic respect, yet be in mental states with different contents. (In response to Twin-Earth thought experiments, some philosophers have, however, attempted to characterize a notion of narrow content, a kind of content that supervenes on intrinsic properties of thinkers.) Content, externalists claim, depends on extrinsic-contextual factors. If externalism is correct, then a psychosemantic theory must examine the relation between mental symbols and the extrinsic, contextual factors that determine contents. Stephen Stich has argued that psychology should eschew psychosemantics and concern itself only with the syntactic properties of mental sentences. Such a psychology could not explain intentional capacities. But Stich urges that computational psychology also eschew that explanatory goal. If, however, psychology is to explain intentional capacities, a psychosemantic theory is needed. Dretske, Fodor, Ruth Millikan, and David Papineau have each independently attempted to provide, in physicalistically respectable terms, foundations for a naturalized externalist theory of the content of mental sentences or internal physical states. Perhaps the leading problem for these theories of content is to explain how the physical and functional facts about a state determine a unique content for it. Appealing to work by Quine and by Kripke, some philosophers argue that such facts will not determine unique contents. Both causal and epistemic concerns have been raised about externalist theories of content. Such theories invite the question whether the property of having a certain content is ever causally relevant. If content is a contextual property of a state that has it, can states have effects in virtue of their having a certain content? This is an important issue because intentional states figure in explanations not only in virtue of their intentional mode (whether they are beliefs, or desires, etc.) but also in virtue of their contents. Consider an everyday belief-desire explanation. The fact that the subject’s belief was that there was milk in the refrigerator and the fact that the subject’s desire was for milk are both essential to the belief and desire explaining why the subject went to the refrigerator. Dretske, who maintains that content depends on a causal-historical context, has attempted to explain how the property of having a certain content can be causally relevant even though the possession of the property depends on causal-historical factors. And various other philosophers have attempted to explain how the causal relevance of content can be squared with the fact that it fails to supervene on intrinsic properties of the subject. A further controversial question is whether externalism is consistent with our having privileged access to what we are thinking.
Conscious states such as pain states, visual experiences, and so on, are such that it is “like” something for the subject of the state to be in them. Such states have a qualitative aspect, a phenomenological character. The what-it-is-like aspects of experiences are called qualia. Qualia pose a serious difficulty for physicalism. Broad argued that one can know all the physical properties of a chemical and how it causally interacts with other physical phenomena and yet not know what it is like to smell it. He concluded that the smell of the chemical is not itself a physical property, but rather an irreducible emergent property. Frank Jackson has recently defended a version of the argument, which has been dubbed the knowledge argument. Jackson argues that a super-scientist, Mary, who knows all the physical and functional facts about color vision, light, and matter, but has never experienced redness since she has spent her entire life in a black and white room, would not know what it is like to visually experience red. He concludes that the physical and functional (topic-neutral) facts do not entail all the facts, and thus materialism is false. In response, Lawrence Nemirow, David Lewis, and others have argued that knowing what it is like to be in a certain conscious state is, in part, a matter of know-how (e.g., to be able to imagine oneself in the state) rather than factual knowledge, and that the failure of knowledge of the physical and functional facts to yield such know-how does not imply the falsity of materialism. Functionalism seems unable to solve the problem of qualia since qualia seem not to be functionally definable. In the 1970s, Fodor and Ned Block argued that two states can have the same causal role, thereby realizing the same functional state, yet the qualia associated with each can be inverted. This is called the problem of inverted qualia. The color spectrum, e.g., might be inverted for two individuals (a possibility raised by Locke), despite their being in the same functional states. They further argued that two states might realize the same functional state, yet the one might have qualia associated with it and the other not. This is called the problem of absent qualia. Sydney Shoemaker has argued that the possibility of absent qualia can be ruled out on functionalist grounds. However, he has also refined the inverted qualia scenario and further articulated the problem it poses for functionalism. Whether functionalism or physicalism can avoid the problems of absent and inverted qualia remains an open question. Thomas Nagel claims that conscious states are subjective: to fully understand them, one must understand what it is like to be in them, but one can do that only by taking up the experiential point of view of a subject in them. Physical states, in contrast, are objective. Physical science attempts to characterize the world in abstraction from the experiential point of view of any subject. According to Nagel, whether phenomenal mental states reduce to physical states turns on whether subjective states reduce to objective states; and, at present, he claims, we have no understanding of how they could. Nagel has suggested that consciousness may be explainable only by appeal to as yet undiscovered basic non-mental, non-physical properties—“proto-mental properties”—the idea being that experiential points of view might be constituted by proto-mental properties together with physical properties. He thus claims that panphysicism is worthy of serious consideration. Frank Jackson, James Van Cleve, and David Chalmers have argued that conscious properties are emergent, i.e., fundamental, irreducible macro-properties; and Chalmers sympathizes with a brand of panphysicism. Colin McGinn claims that while conscious properties are likely reductively explainable by brain properties, our minds seem conceptually closed to the explaining properties: we are unable to conceptualize them, just as a cat is unable to conceptualize a square root. Dennett attempts to explain consciousness in supervenient behaviorist terms. David Rosenthal argues that consciousness is a special case of intentionality —more specifically, that conscious states are just states we can come in a certain direct way to believe we are in. Dretske, William Lycan, and Michael Tye argue that conscious properties are intentional properties and physicalistically reducible. Patricia Churchland argues that conscious phenomena are reducible to neurological phenomena. Brian Loar contends that qualia are identical with either functional or neurological states of the brain; and Christopher Hill argues specifically that qualia are identical with neurological states. Loar and Hill attempt to explain away the appearance of contingency of psychophysical identity claims, but in a way different from the way Kripke attempts to explain the appearance of contingency of ‘Water is H2O’, since they concede that that mode of explanation is unavailable. They appeal to differences in the conceptual roles of neurological and functional concepts by contrast with phenomenal concepts. They argue that while such concepts are different, they answer to the same properties. The nature of consciousness thus remains a matter of dispute. |
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Mind—body dualism |
The doctrine that the soul is distinct from the body is found in Plato and discussed throughout the history of philosophy, but Descartes is considered the father of the modern mind—body problem. He maintained that the essence of the physical is extension in space. Minds are unextended substances and thus are distinct from any physical substances. The essence of a mental substance is to think. This twofold view is called Cartesian dualism. Descartes was well aware of an intimate relationship between mind and the brain. (There is no a priori reason to think that the mind is intimately related to the brain; Aristotle, e.g., did not associate them.) Descartes (mistakenly) thought the seat of the relationship was in the pineal gland. He maintained, however, that our minds are not our brains, lack spatial location, and can continue to exist after the death and destruction of our bodies. Cartesian dualism invites the question: What connects the mind and brain? Causation is Descartes’s answer: states of our minds causally interact with states of our brains. When bodily sensations such as aches, pains, itches, and tickles cause us to moan, wince, scratch, or laugh, they do so by causing brain states (events, processes), which in turn cause bodily movements. In deliberate action, we act on our desires, motives, and intentions to carry out our purposes; and acting on these mental states involves their causing brain states, which in turn cause our bodies to move, thereby causally influencing the physical world. The physical world, in turn, influences our minds through its influence on our brains. Perception of the physical world with five senses—sight, hearing, smell, taste, and touch—involves causal transactions from the physical to the mental: what we perceive (i.e., see, hear, etc.) causes a sense experience (i.e., a visual experience, aural experience, etc.). Thus, Descartes held that there is two-way psychophysical causal interaction: from the mental to the physical (as in action) and from the physical to the mental (as in perception). The conjunction of Cartesian dualism and the doctrine of two-way psychophysical causal interaction is called Cartesian interactionism. Perhaps the most widely discussed difficulty for this view is how states of a non-spatial substance (a mind) can causally interact with states of a substance that is in space (a brain). Such interactions have seemed utterly mysterious to many philosophers. Mystery would remain even if an unextended mind is locatable at a point in space (say, the center of the pineal gland). For Cartesian interactionism would still have to maintain that causal transactions between mental states and brain states are fundamental, i.e., unmediated by any underlying mechanism. Brain states casually interact with mental states, but there is no answer to the question of how they do so. The interactions are brute facts. Many philosophers, including many of Descartes’s contemporaries, have found that difficult to accept.
Malebranche and Leibniz, among others, rejected the possibility of psychophysical causal interaction. They espoused versions of parallelism: the view that the mental and physical realms run in parallel, in that types of mental phenomena co-occur with certain types of physical phenomena, but these co-occurrences never involve causal interactions. On all extant versions, the parallels hold because of God’s creation. Leibniz’s parallelism is preestablished harmony: the explanation of why mental types and certain physical types co-occur is that in the possible world God actualized (i.e., this world) they co-occur. In discussing the relation between the mental and physical realms, Leibniz used the analogy of two synchronized but unconnected clocks. The analogy is, however, somewhat misleading; suggesting causal mechanisms internal to each clock and intramental and intraphysical (causal) transactions. But Leibniz’s monadology doctrine excludes the possibility of such transactions: mental and physical phenomena have no effects even within their own realms. Malebranche is associated with occasionalism, according to which only God, through his continuous activities, causes things to happen: non-divine phenomena never cause anything. Occasionalism differs from preestablished harmony in holding that God is continually engaged in acts of creation; each moment creating the world anew, in such a way that the correlations hold. Both brands of parallelism face formidable difficulties. First, both rest on highly contentious, obscure theological hypotheses. The contention that God exists and the creation stories in question require extensive defense and explanation. God’s relationship to the world can seem at least as mysterious as the relationship Descartes posits between minds and brains. Second, since parallelism denies the possibility of psychophysical interaction, its proponents must offer alternatives to the causal theory of perception and the causal theory of action or else deny that we can perceive and that we can act intentionally. Third, since parallelism rejects intramental causation, it must either deny that reasoning is possible or explain how it is possible without causal connections between thoughts. Fourth, since parallelism rejects physical transactions, it is hard to see how it can allow, e.g., that one physical thing ever moves another; for that would require causing a change in location. Perhaps none of these weighty difficulties is ultimately insuperable; in any case, parallelism has been abandoned.
Empirical research gives every indication that the occurrence of any brain state can, in principle, be causally explained by appeal solely to other physical states. To accommodate this, some philosophers espoused epiphenomenalism, the doctrine that physical states cause mental states, but mental states do not cause anything. (This thesis was discussed under the name ‘conscious automatism’ by Huxley and Hogeson in the late nineteenth century. William James was the first to use the term ‘epiphenomena’ to mean phenomena that lack causal efficacy. And James Ward coined the term ‘epiphenomenalism’ in 1903.) Epiphenomenalism implies that there is only one-way psychophysical action—from the physical to the mental. Since epiphenomenalism allows such causal action, it can embrace the causal theory of perception. However, when combined with Cartesian dualism, epiphenomenalism, like Cartesian interactionism, implies the problematic thesis that states of an extended substance can affect states of an unextended substance. An epiphenomenalist can avoid this problem by rejecting the view that the mind is an unextended substance while maintaining that mental states and events are nonetheless distinct from physical states and events. Still, formidable problems would remain. It is hard to see how epiphenomenalism can allow that we are ever intentional agents. For intentional agency requires acting on reasons, which, according to the causal theory of action, requires a causal connection between reasons and actions. Since epiphenomenalism denies that such causal connections are possible, it must either maintain that our sense of agency is illusory or offer an alternative to the causal theory of action. Similarly, it must explain how thinking is possible given that there are no causal connections between thoughts. |
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Monism |
The dual-aspect theory Many philosophers reject Descartes’s bifurcation of reality into mental and physical substances. Spinoza held a dualattribute theory—also called the dual-aspect theory—according to which the mental and the physical are distinct modes of a single substance, God. The mental and the physical are only two of infinitely many modes of this one substance. Many philosophers opted for a thoroughgoing monism, according to which all of reality is really of one kind. Materialism, idealism, and neutral monism are three brands of monism. Hobbes, a contemporary of Descartes, espoused materialism, the brand of monism according to which everything is material or physical. Berkeley is associated with idealism, the brand of monism according to which everything is mental. He held that both mental and physical phenomena are perceptions in the mind of God. For Hegel’s idealism, everything is part of the World Spirit. The early twentieth-century British philosophers Bradley and McTaggart also held a version of idealism. Neutral monism is the doctrine that all of reality is ultimately of one kind, which is neither mental nor physical. Hume was a neutral monist, maintaining that mental and physical substances are really just bundles of the neutral entities. Versions of neutral monism were later held by Mach and, for a short time, Russell. Russell called his neutral entities sensibilia and claimed that minds and physical objects are logical constructions out of them.
This view, espoused in the twentieth century by, among others, Ayer, argues that all empirical statements are synonymous with statements solely about phenomenal appearances. While the doctrine is about statements, phenomenalism is either a neutral monism or an idealism, depending on whether phenomenal appearances are claimed to be neither mental nor physical or, instead, mental. The required translations of physical statements into phenomenal ones proved not to be forthcoming, however. Chisholm offered a reason why they would not be: what appearances a physical state of affairs (e.g., objects arrayed in a room) has depends both on physical conditions of observation (e.g., lighting) and physical conditions of the perceiver (e.g., of the nervous system). At best, a statement solely about phenomenal appearances is equivalent to one about a physical state of affairs, only when certain physical conditions of observation and certain physical conditions of the perceiver obtain.
Two problems face any monism: it must characterize the phenomena it takes as basic, and it must explain how the fundamental phenomena make up non-basic phenomena. The idealist and neutral monist theories proposed thus far have faltered on one or both counts. Largely because of scientific successes of the twentieth century, such as the rebirth of the atomic theory of matter, and the successes of quantum mechanics in explaining chemistry and of chemistry in turn in explaining much of biology, many philosophers today hold that materialism will ultimately succed where idealism and neutral monism apparently failed. Materialism, however, comes in many different varieties and each faces formidable difficulties.
Ryle ridiculed Cartesianism as the view that there is a ghost in the machine (the body). He claimed that the view that the mind is a substance rests on a category mistake: ‘mind’ is a noun, but does not name an object. Cartesianism confuses the logic of discourse about minds with the logic of discourse about bodies. To have a mind is not to possess a special sort of entity; it is simply to have certain capacities and dispositions. (Compare the thesis that to be alive is to possess not a certain entity, an entelechy or élan vital, but rather certain capacities and dispositions.) Ryle maintained, moreover, that it was a mistake to regard mental states such as belief, desire, and intention as internal causes of behavior. These states, he claimed, are dispositions to behave in overt ways. In part in response to the dualist point that one can understand our ordinary psychological vocabulary (‘belief’, ‘desire’, ‘pain’, etc.) and know nothing about the physical states and events in the brain, logical behaviorism has been proposed as a materialist doctrine that explains this fact. On this view, talk of mental phenomena is shorthand for talk of actual and potential overt bodily behavior (i.e., dispositions to overt bodily behavior). Logical behaviorism was much discussed from roughly the 1930s until the early 1960s. (While Ryle is sometimes counted as a logical behaviorist, he was not committed to the thesis that all mental talk can be translated into behavioral talk.) The translations promised by logical behaviorism appear unachievable. As Putnam and others pointed out, one can fake being in pain and one can be in pain and yet not behave or be disposed to behave as if one were in pain (e.g., one might be paralyzed or might be a “super-spartan”). Logical behaviorism faces similar difficulties in translating sentences about (what Russell called) propositional attitudes (i.e., beliefs that p, desires that p, hopes that p, intentions that p, and the like). Consider the following sample proposal (similar to one offered by Carnap): one believes that the cat is on the mat if and only if one is disposed to assent to ‘The cat is on the mat’. First, the proposed translation meets the condition of being purely behavioral only if assenting is understandable in purely behavioral terms. That is doubtful. The proposal also fails to provide a sufficient or a necessary condition: someone may assent to ‘The cat is on the mat’ and yet not believe the cat is on the mat (for the person may be trying to deceive); and a belief that the cat is on the mat will dispose one to assent to ‘The cat is on the mat’ only if one understands what is being asked, wants to indicate that one believes the cat is on the mat, and so on. But none of these conditions is required for believing that the cat is on the mat. Moreover, to invoke any of these mentalistic conditions defeats the attempt to provide a purely behavioral translation of the belief sentence. Although the project of translation has been abandoned, in recent years Dennett has defended a view in the spirit of logical behaviorism, intentional systems theory: belief-desire talk functions to characterize overall patterns of dispositions to overt behavior (in an environmental context) for the purposes of predicting overt behavior. The theory is sometimes characterized as supervenient behaviorism since it implies that whether an individual has beliefs, desires, intentions and the like supervenes on his dispositions to overt behavior: if two individuals are exactly alike in respect of their dispositions to overt behavior, the one has intentional states if and only if the other does. (This view allows, however, that the contents of an individual’s intentional states—what the individual believes, desires, etc.—may depend on environmental factors. So it is not committed to the supervemence of the contents of intentional states on dispositions to overt behavior. See the discussion of content externalism below.) One objection to this view, due to Ned Block, is that it would mistakenly count as an intentional agent a giant look-up table—“a Blockhead”—that has the same dispositions to peripheral behavior as a genuine intentional agent. (A look-up table is a simple mechanical device that looks up preprogrammed responses.)
In the early 1950s, Herbert Feigl claimed that mental states are brain states. He pointed out that if mental properties or state types are merely nomologically correlated with physical properties or state types, the connecting laws would be “nomological danglers”: irreducible to physical laws, and thus additional fundamental laws. According to the identity theory, the connecting laws are not fundamental laws (and so not nomological danglers) since they can be explained by identifying the mental and physical properties in question. In the late 1950s and the early 1960s, the philosopher Smart and the psychologist U.T. Place defended the materialist view that sensations are identical with brain processes. Smart claimed that while mental terms differ in meaning from physical terms, scientific investigation reveals that they have the same referents as certain physical terms. (Compare the fact that while ‘the Morning Star’ and ‘the Evening Star’ differ in meaning empirical investigation reveals the same referent: Venus.) Smart and Place claimed that feeling pain, e.g., is some brain process, exactly which one to be determined by scientific investigation. Smart claimed that sensation talk is paraphraseable in topic-neutral terms; i.e., in terms that leave open whether sensational properties are mental or physical. ‘I have an orange afterimage’ is paraphraseable (roughly) as: ‘There is something going on like what is going on when I have my eyes open, am awake, and there is an orange illuminated in good light in front of me, i.e., when I really see an orange’. The description is topic-neutral since it leaves open whether what is going on is mental or physical. Smart maintained that scientific investigation reveals that what in fact meets the topic-neutral description is a brain process. He held that psychophysical identity statements such as ‘Pain is C-fiber firing’ are contingent, likening these to, e.g., ‘Lightning is electrical discharge’, which is contingent and knowable only through empirical investigation.
This brand of materialism was defended in the late 1960s and the early 1970s by Armstrong and others. On this view, mental states are states that are apt to produce a certain range of behavior. Central state materialists maintain that scientific investigation reveals that such states are states of the central nervous system, and thus that mental states are contingently identical with states of the central nervous system. Unlike logical behaviorism, central state materialism does not imply that mental sentences can be translated into physical sentences. Unlike both logical behaviorism and intentional systems theory, central state materialism implies that mental states are actual internal states with causal effects. And unlike Cartesian interactionism, it holds that psychophysical interaction is just physical causal interaction. Some central state materialists held in addition that the mind is the brain. However, if the mind were the brain, every change in the brain would be a change in the mind; and that seems false: not every little brain change amounts to a change of mind. Indeed, the mind ceases to exist when brain death occurs, while the brain continues to exist. The moral that most materialists nowadays draw from such considerations is that the mind is not any physical substance, since it is not a substance of any sort. To have a mind is not to possess a special substance, but rather to have certain capacities—to think, feel, etc. To that extent, Ryle was right. However, central state materialists insist that the properly functioning brain is the material seat of mental capacities, that the exercise of mental capacities consists of brain processes, and that mental states are brain states that can produce behavior. Epistemological objections have been raised to identity theories. As self-conscious beings, we have a kind of privileged access to our own mental states. The exact avenue of privileged access, whether it is introspection or not, is controversial. But it has seemed to many philosophers that our access to our own mental states is privileged in being open only to us, whereas we lack any privileged access to the states of our central nervous systems. We come to know about central nervous system states in the same way we come to know about the central nervous system states of others. So, against central state materialism and the identity theory, it is claimed that mental states cannot be states of our central nervous systems. Taking privileged access to imply that we have incorrigible knowledge of our conscious mental states, and despairing of squaring privileged access so understood with materialism, Rorty advocated eliminative materialism, the thesis that there actually are no mental phenomena. A more common materialist response, however, is to deny that privileged access entails incorrigibility and to maintain that privileged access is compatible with materialism. Some materialists maintain that while certain types of mental states (e.g., sensations) are types of neurological states, it will be knowable only by empirical investigation that they are. Suppose pain is a neural state N. It will be only a posteriori knowable that pain is N. Via the avenue of privileged access, one comes to believe that one is in a pain state, but not that one is in an N-state. One can believe one is in a pain state without believing that one is in an N-state because the concept of pain is different from the concept of N. Nevertheless, pain is N. (Compare the fact that while water is H2O, the concept of water is different from that of H2O. Thus, while water is H2O, one can believe there is water in the glass without believing that there is H2O in it. The avenue of privileged access presents N conceptualized as pain, but never as neurological state N. The avenue of privileged access involves the exercise of mental, but not neurophysiological, concepts. However, our mental concepts answer to—apply in virtue of—the same properties (state types) as do certain of our neurophysiological concepts. The identity theory and central state materialism both hold that there are contingent psychophysical property and type identities. Some theorists in this tradition tried to distinguish a notion of theoretical identity from the notion of strict identity. They held that mental states are theoretically, but not strictly, identical with brain states. Against any such distinction, Kripke argued that identities are metaphysically necessary, i.e., hold in every possible world. If A = B, then necessarily A = B. Kripke acknowledged that there can be contingent statements of identity. But such statements, he argued, will employ at least one term that is not a rigid designator, i.e., a term that designates the same thing in every world in which it designates anything. Thus, since ‘the inventor of bifocals’ is a non-rigid designator, ‘Benjamin Franklin is the inventor of bifocals’ is contingent. While Franklin is the inventor of bifocals, he might not have been. However, statements of identity in which the identity sign is flanked by rigid designators are, if true, metaphysically necessary. Kripke held that proper names are rigid designators, and hence, the true identity statement ‘Cicero is Tully’ is metaphysically necessary. Nonetheless, a metaphysically necessary identity statement can be knowable only a posteriori. Indeed, ‘Cicero is Tully’ is knowable only a posteriori. Both ‘water’ and ‘H2O’, he maintained, are rigid designators: each designates the same kind of stuff in every possible world. And he thus maintained that it is metaphysically necessary that water is H2O, despite its not being a priori knowable that water is H2O. On Kripke’s view, any psychophysical identity statement that employs mental terms and physical terms that are rigid designators will also be metaphysically necessary, if true. Central state materialists maintain that mental concepts are equivalent to concepts whose descriptive content is the state that is apt to produce such-and-such behavior in such-and-such circumstances. These defining descriptions for mental concepts are intended to be meaning-giving, not contingent reference-fixing descriptions; they are, moreover, not rigid designators. Thus, the central state materialists can concede that all identities are necessary, but maintain that psychophysical claims of identity are contingent claims of identity since the mental terms that figure in those statements are not rigid designators. However, Kripke maintained that our concepts of sensations and other qualitative states are not equivalent to the sorts of descriptions in question. The term ‘pain’, he maintained, is a rigid designator. This position might be refuted by a successful functional analysis of the concept of pain in physical and/or topic-neutral terms. However, no successful analysis of this sort has yet been produced. (See the section on consciousness below.) A materialist can grant Kripke that ‘pain’ is a rigid designator and claim that a statement such as ‘Pain is C-fiber firing’ will be metaphysically necessary if true, but only a posteriori knowable. However, Kripke raised a formidable problem for this materialism. He pointed out that if a statement is metaphysically necessary but only a posteriori knowable, its appearance of contingency calls for explanation. Despite being metaphysically necessary, ‘Water is H2O’ appears contingent. According to Kripke, we explain this appearance by noting that one can coherently imagine a world in which something has all the phenomenal properties of water, and so is an “epistemic counterpart” of it, yet is not H2O. The fact that we can coherently imagine such epistemic counterparts explains why ‘Water is H2O’ appears contingent. But no such explanation is available for (e.g.) ‘Pain is C-fiber firing’. For an epistemic counterpart of pain, something with the phenomenal properties of pain—the feel of pain—is pain. Something can look, smell, taste, and feel like water yet not be water. But whatever feels like pain is pain: pain is a feeling. In contrast, we can explain the apparent contingency of claims like ‘Water is H2O’ because water is not constituted by its phenomenal properties; our concept of water allows that it may have a “hidden essence,” i.e., an essential microstructure. If Kripke is right, then anyone who maintains that a statement of identity concerning a type of bodily sensation and a type of physical state is metaphysically necessary yet a posteriori, must explain the appearance of contingency in a way that differs from the way Kripke explains the appearance of contingency of ‘Water is H2O’. This is a formidable challenge. (The final section, on consciousness, sketches some materialist responses to it.) The general issue of property and state type identity is controversial. The claim that water is H2O despite the fact that the concept of water is distinct from the concept of H2O seems plausible. However, property or state type identity is more controversial than the identity of types of substances. For properties or state types, there are no generally accepted “non-duplication principles” —to use a phrase of David Lewis’s. (A non-duplication principle for A’s will say that no two A’s can be exactly alike in a certain respect; e.g., no two sets can have exactly the same members.) It is widely denied, for instance, that no two properties can be possessed by exactly the same things. Two properties, it is claimed, can be possessed by the same things; likewise, two state types can occur in the same space-time regions. Even assuming that mental concepts are distinct from physical concepts, the issue of whether mental state types are physical state types raises the controversial issue of the non-duplication principle for state types.
Token physicalism is the thesis that every particular is physical. Type physicalism is the thesis that every type or kind of entity is physical; thus, the identity thesis and central state materialism are type physicalist theses since they imply that types of mental states are types of physical states. Type physicalism implies token physicalism: given the former, every token falls under some physical type, and therefore is token-token identical with some token of a physical type. But token physicalism does not imply type physicalism; the former leaves open whether physical tokens fall under non-physical types. Some doctrines billed as materialist or physicalist embrace token epiphenomenalism, but reject type physicalism.
This form of materialism implies token physicalism, but denies type physicalism and, as well, that mental types (properties, etc.) are reducible to physical types. This doctrine has been discussed since at least the late nineteenth century and was widely discussed in the first third of the twentieth century. The British philosophers George Henry Lewes, Samuel Alexander, Lloyd Morgan, and C.D. Broad all held or thought plausible a certain version of non-reductive materialism. They held or sympathized with the view that every substance either is or is wholly made up of physical particles, that the well-functioning brain is the material seat of mental capacities, and that token mental states (events, processes, etc.) are token neurophysiological states (events, processes, etc.). However, they either held or thought plausible the view that mental capacities, properties, etc., emerge from, and thus do not reduce to, physical capacities, properties, etc. Lewes coined the term ‘emergence’; and Broad later labeled the doctrine emergent materialism. Emergent materialists maintain that laws correlating mental and physical properties are irreducible. (These laws would be what Feigl called nomological danglers.) Emergentists maintain that, despite their untidiness, such laws must be accepted with natural piety. Davidson’s doctrine of anomalous monism is a current brand of non-reductive materialism. He explicitly formulates this materialist thesis for events; and his irreducibility thesis is restricted to intentional mental types—e.g., believings, desirings, and intendings. Anomalous monism says that every event token is physical, but that intentional mental predicates and concepts (ones expressing propositional attitudes) do not reduce, by law or definition, to physical predicates or concepts. Davidson offers an original argument for this irreducibility thesis. Mental predicates and concepts are, he claims, governed by constitutive principles of rationality, but physical predicates and concepts are not. This difference, he contends, excludes the possibility of reduction of mental predicates and concepts to physical ones. Davidson denies, moreover, that there are strict psychological or psychophysical laws. He calls the conjunction of this thesis and his irreducibility thesis the principle of the anomalism of the mental. His argument for token physicalism (for events) appeals to the principle of the anomalism of the mental and to the principle of the nomological character of causality: when two events are causally related, they are subsumed by a strict law. He maintains that all strict laws are physical. Given that claim, and given the principle of the nomological character of causality, it follows that every event that is a cause or effect is a physical event. On this view, psychophysical causation is just causation between physical events. Stephen Schiffer has also maintained a non-reductive materialism, one he calls ontological physicalism and sentential dualism: every particular is physical, but mental truths are irreducible to physical truths. Non-reductive materialism presupposes that mental state (event) tokens can fall under physical state types and, thereby, count as physical state tokens. This presupposition is controversial; no uncontroversial non-duplication principle for state tokens settles the issue. Suppose, however, that mental state tokens are physical state tokens, despite mental state types not being physical state types. The issue of how mental state types and physical state types are related remains. Suppose that some physical token x is of a mental type M (say, a belief that the cat is on the mat) and some other physical token y is not of type M. There must, it seems, be some difference between x and y in virtue of which x is, and y is not, of type M. Otherwise, it is simply a brute fact that x is and y is not of type M. That, however, seems implausible. The claim that certain physical state tokens fall under mental state types simply as a matter of brute fact would leave the difference in question utterly mysterious. But if it is not a brute fact, then there is some explanation of why a certain physical state is a mental state of a certain sort. The non-reductive materialist owes us an explanation that does not imply psychophysical reduction. Moreover, even though the non-reductive materialist can claim that mental states are causes because they are physical states with physical effects, there is some question whether mental state types are relevant to causal relations. Suppose every state is a physical state. Given that physical states causally interact in virtue of falling under physical types, it follows that whenever states causally interact they do so in virtue of falling under physical types. That raises the issue of whether states are ever causes in virtue of falling under mental types. Type epiphenomenalism is the thesis that no state can cause anything in virtue of falling under a mental type. Token epiphenomenalism, the thesis that no mental state can cause anything, implies type epiphenomenalism, but not conversely. Non-reductive materialists are not committed to token physicalism. However, token epiphenomenalism may be false but type epiphenomenalism true since mental states may be causes only in virtue of falling under physical types, never in virtue of falling under mental types. Broad raised the issue of type epiphenomenalism and discussed whether emergent materialism is committed to it. Ted Honderich, Jaegwon Kim, Ernest Sosa, and others have in recent years raised the issue of whether non-reductive materialism is committed to type epiphenomenalism. Brian McLaughlin has argued that the claim that an event acts as a cause in virtue of falling under a certain physical type is consistent with the claim that it also acts as a cause in virtue of falling under a certain mental type, even when the mental type is not identical with the physical type. But even if this is so, the relationship between mental types and physical types must be addressed. Ernest LePore and Barry Loewer, Frank Jackson and Philip Pettit, Stephen Yablo, and others have attempted to characterize a relation between mental types and physical types that allows for the causal relevance of mental types. But whether there is a relation between mental and physical properties that is both adequate to secure the causal relevance of mental properties and available to non-reductive materialists remains an open question. Davidson’s anomalous monism may appear to be a kind of dual-aspect theory: there are events and they can have two sorts of autonomous aspects, mental and physical. However, while Davidson holds that mental properties (or types) do not reduce to physical ones, he also holds that the mental properties of an event depend on its physical properties in that the former supervene on the latter in this sense: no two events can be exactly alike in every physical respect and yet differ in some mental respect. This proposal introduced the notion of supervenience into contem- porary philosophy of mind. Often non-reductive materialists argue that mental properties (types) supervene on physical properties (types). Kim, however, has distinguished various supervenience relations, and argues that some are too weak to count as versions of materialism (as opposed to, say, dual-aspect theory), while other supervenience relations are too strong to use to formulate non-reductive materialism since they imply reducibility. According to Kim, non-reductive materialism is an unstable position.
Several philosophers have in recent years attempted to define the thesis of materialism using a global supervenience thesis. Their aim is not to formulate a brand of non-reductive materialism; they maintain that their supervenience thesis may well imply reducibility. Their aim is, rather, to formulate a thesis to which anyone who counts as a genuine materialist must subscribe. David Lewis has maintained that materialism is true if and only if any non-alien possible worlds that are physically indiscernible are mentally indiscernible as well. Non-alien possible worlds are worlds that have exactly the same perfectly natural properties as the actual world. Frank Jackson has offered this proposal: materialism is true if and only if any minimal physical duplicate of the actual world is a duplicate simpliciter of the actual world. A world is a physical duplicate of the actual world if and only if it is exactly like the actual world in every physical respect (physical particular for physical particular, physical property for physical property, physical relation for physical relation, etc.); and a world is a duplicate simpliciter of the actual world if and only if it is exactly like the actual world in every respect. A minimal physical duplicate of the actual world is a physical duplicate that contains nothing else (by way of particulars, kinds, properties, etc.) than it must in order to be a physical duplicate of the actual world. Two questions arise for any formulation of the thesis of materialism. Is it adequate to materialism? And, if it is, is it true? |
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Functionalism |
The nineteenth-century British philosopher George Henry Lewes maintained that while not every neurological event is mental, every mental event is neurological. He claimed that what makes certain neurological events mental events is their causal role in the organism. This is a very early version of functionalism, nowadays a leading approach to the mind—body problem. Functionalism implies an answer to the question of what makes a state token a mental state of a certain kind M: namely, that it is an instance of some functional state type identical with M. There are two versions of this proposal. On one, a mental state type M of a system will be identical with the state type that plays a certain causal role R in the system. The description ‘the state type that plays R in the system’ will be a nonrigid designator; moreover, different state types may play R in different organisms, in which case the mental state is multiply realizable. On the second version, a mental state type M is identical with a second-order state type, the state of being in some first-order state that plays causal role R. More than one first-order state may play role R, and thus M may be multiply realizable. On either version, if the relevant causal roles are specifiable in physical or topic-neutral terms, then the functional definitions of mental state types will be, in principle, physically reductive. Since the roles would be specified partly in topic-neutral terms, there may well be possible worlds in which the mental states are realized by non-physical states; thus, functionalism does not imply token physicalism. However, functionalists typically maintain that, on the empirical evidence, mental states are realized (in our world) only by physical states. Functionalism comes in many varieties. Smart’s topic-neutral analysis of our talk of sensations is in the spirit of functionalism. And Armstrong’s central state materialism counts as a kind of functionalism since it maintains that mental states are states apt to produce a certain range of behavior, and thus identifies states as mental states by their performing this causal role. However, functionalists today typically hold that the defining causal roles include causal roles vis-à-vis input state types, as well as output state types, and also vis-à-vis other internal state types of the system in question. In the 1960s David Lewis proposed a functionalist theory, analytical functionalism, according to which definitions of mental predicates such as ‘belief’, ‘desire’, and the like (though not predicates such as ‘believes that p’ or ‘desires that q’) can be obtained by conjoining the platitudes of commonsense psychology and formulating the Ramsey sentence for the conjunction. The relevant Ramsey sentence is a second-order quantificational sentence that quantifies over the mental predicates in the conjunction of commonsense psychological platitudes, and from it one can derive definitions of the mental predicates. On this view, it will be analytic that a certain mental state (e.g., belief) is the state that plays a certain causal role vis-à-vis other states; and it is a matter of empirical investigation what state plays the role. Lewis claimed that such investigation reveals that the state types that play the roles in question are physical states. In the early 1960s, Putnam proposed a version of scientific functionalism, machine state functionalism: according to this view, mental states are types of Turing machine table states. Turing machines are mechanical devices consisting of a tape with squares on it that either are blank or contain symbols, and an executive that can move one square to the left, or one square to the right, or stay where it is. And it can either write a symbol on a square, erase a symbol on a square, or leave the square as it is. (According to the Church-Turing thesis, every computable function can be computed by a Turing machine.) Now there are two functions specifying such a machine: one from input states to output states, the other from input states to input states. And these functions are expressible by counterfactuals (e.g., ‘If the machine is in state s1 and receives input I, it will emit output O and enter state s2’). Machine tables are specified by the counterfactuals that express the functions in question. So the main idea of machine state functionalism is that any given mental type is definable as the state type that participates in certain counterfactual relationships specified in terms of purely formal, and so not semantically interpreted, state types. Any system whose inputs, outputs, and internal states are counterfactually related in the way characterized by a machine table is a realization of that table. This version of machine state functionalism has been abandoned: no one maintains that the mind has the architecture of a Turing machine. However, computational psychology, a branch of cognitive psychology, presupposes a scientific functionalist view of cognitive states: it takes the mind to have a computational architecture. (See the section on cognitive psychology below.) Functionalism—the view that what makes a state a realization of a mental state is its playing a certain causal role—remains a leading theory of mind. But functionalism faces formidable difficulties. Block has pinpointed one. On the one hand, if the input and output states that figure in the causal role alleged to define a certain mental state are specified in insufficient detail, the functional definition will be too liberal: it will mistakenly classify certain states as of that mental type. On the other hand, if the input and output states are specified in too much detail, the functional definition will be chauvinistic: it will fail to count certain states as instances of the mental state that are in fact such instances. Moreover, it has also been argued that functionalism cannot capture conscious states since types of conscious states do not admit of functional definitions. |
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Cognitive psychology, content, and consciousness |
Cognitive psychology Many claim that one aim of cognitive psychology is to provide explanations of intentional capacities, capacities to be in intentional states (e.g., believing) and to engage in intentional activities (e.g., reasoning). Fodor has argued that classical cognitive psychology postulates a cognitive architecture that includes a language of thought: a system of mental representation with a combinatorial syntax and semantics, and computational processes defined over these mental representations in virtue of their syntactic structures. On this view, cognition is rule-governed symbol manipulation. Mental symbols have meanings, but they participate in computational processes solely in virtue of their syntactic or formal properties. The mind is, so to speak, a syntactic engine. The view implies a kind of content parallelism: syntax-sensitive causal transitions between symbols will preserve semantic coherence. Fodor has maintained that, on this language-of-thought view of cognition (the classical view), being in a beliefthat-p state can be understood as consisting in bearing a computational relation (one that is constitutive of belief) to a sentence in the language of thought that means that p; and similarly for desire, intention, and the like. The explanation of intentional capacities will be provided by a computational theory for mental sentences in conjunction with a psychosemantic theory, a theory of meaning for mental sentences. A research program in cognitive science called connectionism postulates networks of neuron-like units. The units can be either on or off, or can have continuous levels of activation. Units are connected, the connections have various degrees of strength, and the connections can be either inhibitory or excitatory. Connectionism has provided fruitful models for studying how neural networks compute information. Moreover, connectionists have had much success in modeling pattern recognition tasks (e.g., facial recognition) and tasks consisting of learning categories from examples. Some connectionists maintain that connectionism will yield an alternative to the classical language-of-thought account of intentional states and capacities. However, some favor a mixed-models approach to cognition: some cognitive capacities are symbolic, some connectionist. And some hold that connectionism will yield an implementational architecture for a symbolic cognitive architecture, one that will help explain how a symbolic cognitive architecture is realized in the nervous system.
Many today hold that Twin-Earth thought experiments by Putnam and Tyler Burge show that the contents of a subject’s mental states do not supervene on intrinsic properties of the subject: two individuals can be exactly alike in every intrinsic respect, yet be in mental states with different contents. (In response to Twin-Earth thought experiments, some philosophers have, however, attempted to characterize a notion of narrow content, a kind of content that supervenes on intrinsic properties of thinkers.) Content, externalists claim, depends on extrinsic-contextual factors. If externalism is correct, then a psychosemantic theory must examine the relation between mental symbols and the extrinsic, contextual factors that determine contents. Stephen Stich has argued that psychology should eschew psychosemantics and concern itself only with the syntactic properties of mental sentences. Such a psychology could not explain intentional capacities. But Stich urges that computational psychology also eschew that explanatory goal. If, however, psychology is to explain intentional capacities, a psychosemantic theory is needed. Dretske, Fodor, Ruth Millikan, and David Papineau have each independently attempted to provide, in physicalistically respectable terms, foundations for a naturalized externalist theory of the content of mental sentences or internal physical states. Perhaps the leading problem for these theories of content is to explain how the physical and functional facts about a state determine a unique content for it. Appealing to work by Quine and by Kripke, some philosophers argue that such facts will not determine unique contents. Both causal and epistemic concerns have been raised about externalist theories of content. Such theories invite the question whether the property of having a certain content is ever causally relevant. If content is a contextual property of a state that has it, can states have effects in virtue of their having a certain content? This is an important issue because intentional states figure in explanations not only in virtue of their intentional mode (whether they are beliefs, or desires, etc.) but also in virtue of their contents. Consider an everyday belief-desire explanation. The fact that the subject’s belief was that there was milk in the refrigerator and the fact that the subject’s desire was for milk are both essential to the belief and desire explaining why the subject went to the refrigerator. Dretske, who maintains that content depends on a causal-historical context, has attempted to explain how the property of having a certain content can be causally relevant even though the possession of the property depends on causal-historical factors. And various other philosophers have attempted to explain how the causal relevance of content can be squared with the fact that it fails to supervene on intrinsic properties of the subject. A further controversial question is whether externalism is consistent with our having privileged access to what we are thinking.
Conscious states such as pain states, visual experiences, and so on, are such that it is “like” something for the subject of the state to be in them. Such states have a qualitative aspect, a phenomenological character. The what-it-is-like aspects of experiences are called qualia. Qualia pose a serious difficulty for physicalism. Broad argued that one can know all the physical properties of a chemical and how it causally interacts with other physical phenomena and yet not know what it is like to smell it. He concluded that the smell of the chemical is not itself a physical property, but rather an irreducible emergent property. Frank Jackson has recently defended a version of the argument, which has been dubbed the knowledge argument. Jackson argues that a super-scientist, Mary, who knows all the physical and functional facts about color vision, light, and matter, but has never experienced redness since she has spent her entire life in a black and white room, would not know what it is like to visually experience red. He concludes that the physical and functional (topic-neutral) facts do not entail all the facts, and thus materialism is false. In response, Lawrence Nemirow, David Lewis, and others have argued that knowing what it is like to be in a certain conscious state is, in part, a matter of know-how (e.g., to be able to imagine oneself in the state) rather than factual knowledge, and that the failure of knowledge of the physical and functional facts to yield such know-how does not imply the falsity of materialism. Functionalism seems unable to solve the problem of qualia since qualia seem not to be functionally definable. In the 1970s, Fodor and Ned Block argued that two states can have the same causal role, thereby realizing the same functional state, yet the qualia associated with each can be inverted. This is called the problem of inverted qualia. The color spectrum, e.g., might be inverted for two individuals (a possibility raised by Locke), despite their being in the same functional states. They further argued that two states might realize the same functional state, yet the one might have qualia associated with it and the other not. This is called the problem of absent qualia. Sydney Shoemaker has argued that the possibility of absent qualia can be ruled out on functionalist grounds. However, he has also refined the inverted qualia scenario and further articulated the problem it poses for functionalism. Whether functionalism or physicalism can avoid the problems of absent and inverted qualia remains an open question. Thomas Nagel claims that conscious states are subjective: to fully understand them, one must understand what it is like to be in them, but one can do that only by taking up the experiential point of view of a subject in them. Physical states, in contrast, are objective. Physical science attempts to characterize the world in abstraction from the experiential point of view of any subject. According to Nagel, whether phenomenal mental states reduce to physical states turns on whether subjective states reduce to objective states; and, at present, he claims, we have no understanding of how they could. Nagel has suggested that consciousness may be explainable only by appeal to as yet undiscovered basic non-mental, non-physical properties—“proto-mental properties”—the idea being that experiential points of view might be constituted by proto-mental properties together with physical properties. He thus claims that panphysicism is worthy of serious consideration. Frank Jackson, James Van Cleve, and David Chalmers have argued that conscious properties are emergent, i.e., fundamental, irreducible macro-properties; and Chalmers sympathizes with a brand of panphysicism. Colin McGinn claims that while conscious properties are likely reductively explainable by brain properties, our minds seem conceptually closed to the explaining properties: we are unable to conceptualize them, just as a cat is unable to conceptualize a square root. Dennett attempts to explain consciousness in supervenient behaviorist terms. David Rosenthal argues that consciousness is a special case of intentionality —more specifically, that conscious states are just states we can come in a certain direct way to believe we are in. Dretske, William Lycan, and Michael Tye argue that conscious properties are intentional properties and physicalistically reducible. Patricia Churchland argues that conscious phenomena are reducible to neurological phenomena. Brian Loar contends that qualia are identical with either functional or neurological states of the brain; and Christopher Hill argues specifically that qualia are identical with neurological states. Loar and Hill attempt to explain away the appearance of contingency of psychophysical identity claims, but in a way different from the way Kripke attempts to explain the appearance of contingency of ‘Water is H2O’, since they concede that that mode of explanation is unavailable. They appeal to differences in the conceptual roles of neurological and functional concepts by contrast with phenomenal concepts. They argue that while such concepts are different, they answer to the same properties. The nature of consciousness thus remains a matter of dispute. |
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Cartesian dualism |
The doctrine that the soul is distinct from the body is found in Plato and discussed throughout the history of philosophy, but Descartes is considered the father of the modern mind—body problem. He maintained that the essence of the physical is extension in space. Minds are unextended substances and thus are distinct from any physical substances. The essence of a mental substance is to think. This twofold view is called Cartesian dualism. Descartes was well aware of an intimate relationship between mind and the brain. (There is no a priori reason to think that the mind is intimately related to the brain; Aristotle, e.g., did not associate them.) Descartes (mistakenly) thought the seat of the relationship was in the pineal gland. He maintained, however, that our minds are not our brains, lack spatial location, and can continue to exist after the death and destruction of our bodies. Cartesian dualism invites the question: What connects the mind and brain? Causation is Descartes’s answer: states of our minds causally interact with states of our brains. When bodily sensations such as aches, pains, itches, and tickles cause us to moan, wince, scratch, or laugh, they do so by causing brain states (events, processes), which in turn cause bodily movements. In deliberate action, we act on our desires, motives, and intentions to carry out our purposes; and acting on these mental states involves their causing brain states, which in turn cause our bodies to move, thereby causally influencing the physical world. The physical world, in turn, influences our minds through its influence on our brains. Perception of the physical world with five senses—sight, hearing, smell, taste, and touch—involves causal transactions from the physical to the mental: what we perceive (i.e., see, hear, etc.) causes a sense experience (i.e., a visual experience, aural experience, etc.). Thus, Descartes held that there is two-way psychophysical causal interaction: from the mental to the physical (as in action) and from the physical to the mental (as in perception). The conjunction of Cartesian dualism and the doctrine of two-way psychophysical causal interaction is called Cartesian interactionism. Perhaps the most widely discussed difficulty for this view is how states of a non-spatial substance (a mind) can causally interact with states of a substance that is in space (a brain). Such interactions have seemed utterly mysterious to many philosophers. Mystery would remain even if an unextended mind is locatable at a point in space (say, the center of the pineal gland). For Cartesian interactionism would still have to maintain that causal transactions between mental states and brain states are fundamental, i.e., unmediated by any underlying mechanism. Brain states casually interact with mental states, but there is no answer to the question of how they do so. The interactions are brute facts. Many philosophers, including many of Descartes’s contemporaries, have found that difficult to accept. |
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Parallelism |
Malebranche and Leibniz, among others, rejected the possibility of psychophysical causal interaction. They espoused versions of parallelism: the view that the mental and physical realms run in parallel, in that types of mental phenomena co-occur with certain types of physical phenomena, but these co-occurrences never involve causal interactions. On all extant versions, the parallels hold because of God’s creation. Leibniz’s parallelism is preestablished harmony: the explanation of why mental types and certain physical types co-occur is that in the possible world God actualized (i.e., this world) they co-occur. In discussing the relation between the mental and physical realms, Leibniz used the analogy of two synchronized but unconnected clocks. The analogy is, however, somewhat misleading; suggesting causal mechanisms internal to each clock and intramental and intraphysical (causal) transactions. But Leibniz’s monadology doctrine excludes the possibility of such transactions: mental and physical phenomena have no effects even within their own realms. Malebranche is associated with occasionalism, according to which only God, through his continuous activities, causes things to happen: non-divine phenomena never cause anything. Occasionalism differs from preestablished harmony in holding that God is continually engaged in acts of creation; each moment creating the world anew, in such a way that the correlations hold. Both brands of parallelism face formidable difficulties. First, both rest on highly contentious, obscure theological hypotheses. The contention that God exists and the creation stories in question require extensive defense and explanation. God’s relationship to the world can seem at least as mysterious as the relationship Descartes posits between minds and brains. Second, since parallelism denies the possibility of psychophysical interaction, its proponents must offer alternatives to the causal theory of perception and the causal theory of action or else deny that we can perceive and that we can act intentionally. Third, since parallelism rejects intramental causation, it must either deny that reasoning is possible or explain how it is possible without causal connections between thoughts. Fourth, since parallelism rejects physical transactions, it is hard to see how it can allow, e.g., that one physical thing ever moves another; for that would require causing a change in location. Perhaps none of these weighty difficulties is ultimately insuperable; in any case, parallelism has been abandoned. |
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Epiphenomenalism |
Empirical research gives every indication that the occurrence of any brain state can, in principle, be causally explained by appeal solely to other physical states. To accommodate this, some philosophers espoused epiphenomenalism, the doctrine that physical states cause mental states, but mental states do not cause anything. (This thesis was discussed under the name ‘conscious automatism’ by Huxley and Hogeson in the late nineteenth century. William James was the first to use the term ‘epiphenomena’ to mean phenomena that lack causal efficacy. And James Ward coined the term ‘epiphenomenalism’ in 1903.) Epiphenomenalism implies that there is only one-way psychophysical action—from the physical to the mental. Since epiphenomenalism allows such causal action, it can embrace the causal theory of perception. However, when combined with Cartesian dualism, epiphenomenalism, like Cartesian interactionism, implies the problematic thesis that states of an extended substance can affect states of an unextended substance. An epiphenomenalist can avoid this problem by rejecting the view that the mind is an unextended substance while maintaining that mental states and events are nonetheless distinct from physical states and events. Still, formidable problems would remain. It is hard to see how epiphenomenalism can allow that we are ever intentional agents. For intentional agency requires acting on reasons, which, according to the causal theory of action, requires a causal connection between reasons and actions. Since epiphenomenalism denies that such causal connections are possible, it must either maintain that our sense of agency is illusory or offer an alternative to the causal theory of action. Similarly, it must explain how thinking is possible given that there are no causal connections between thoughts. |
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The dual-aspect theory |
Many philosophers reject Descartes’s bifurcation of reality into mental and physical substances. Spinoza held a dualattribute theory—also called the dual-aspect theory—according to which the mental and the physical are distinct modes of a single substance, God. The mental and the physical are only two of infinitely many modes of this one substance. Many philosophers opted for a thoroughgoing monism, according to which all of reality is really of one kind. Materialism, idealism, and neutral monism are three brands of monism. Hobbes, a contemporary of Descartes, espoused materialism, the brand of monism according to which everything is material or physical. Berkeley is associated with idealism, the brand of monism according to which everything is mental. He held that both mental and physical phenomena are perceptions in the mind of God. For Hegel’s idealism, everything is part of the World Spirit. The early twentieth-century British philosophers Bradley and McTaggart also held a version of idealism. Neutral monism is the doctrine that all of reality is ultimately of one kind, which is neither mental nor physical. Hume was a neutral monist, maintaining that mental and physical substances are really just bundles of the neutral entities. Versions of neutral monism were later held by Mach and, for a short time, Russell. Russell called his neutral entities sensibilia and claimed that minds and physical objects are logical constructions out of them. |
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Phenomenalism |
This view, espoused in the twentieth century by, among others, Ayer, argues that all empirical statements are synonymous with statements solely about phenomenal appearances. While the doctrine is about statements, phenomenalism is either a neutral monism or an idealism, depending on whether phenomenal appearances are claimed to be neither mental nor physical or, instead, mental. The required translations of physical statements into phenomenal ones proved not to be forthcoming, however. Chisholm offered a reason why they would not be: what appearances a physical state of affairs (e.g., objects arrayed in a room) has depends both on physical conditions of observation (e.g., lighting) and physical conditions of the perceiver (e.g., of the nervous system). At best, a statement solely about phenomenal appearances is equivalent to one about a physical state of affairs, only when certain physical conditions of observation and certain physical conditions of the perceiver obtain. |
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Materialism |
Two problems face any monism: it must characterize the phenomena it takes as basic, and it must explain how the fundamental phenomena make up non-basic phenomena. The idealist and neutral monist theories proposed thus far have faltered on one or both counts. Largely because of scientific successes of the twentieth century, such as the rebirth of the atomic theory of matter, and the successes of quantum mechanics in explaining chemistry and of chemistry in turn in explaining much of biology, many philosophers today hold that materialism will ultimately succed where idealism and neutral monism apparently failed. Materialism, however, comes in many different varieties and each faces formidable difficulties. |
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Logical behaviorism |
Ryle ridiculed Cartesianism as the view that there is a ghost in the machine (the body). He claimed that the view that the mind is a substance rests on a category mistake: ‘mind’ is a noun, but does not name an object. Cartesianism confuses the logic of discourse about minds with the logic of discourse about bodies. To have a mind is not to possess a special sort of entity; it is simply to have certain capacities and dispositions. (Compare the thesis that to be alive is to possess not a certain entity, an entelechy or élan vital, but rather certain capacities and dispositions.) Ryle maintained, moreover, that it was a mistake to regard mental states such as belief, desire, and intention as internal causes of behavior. These states, he claimed, are dispositions to behave in overt ways. In part in response to the dualist point that one can understand our ordinary psychological vocabulary (‘belief’, ‘desire’, ‘pain’, etc.) and know nothing about the physical states and events in the brain, logical behaviorism has been proposed as a materialist doctrine that explains this fact. On this view, talk of mental phenomena is shorthand for talk of actual and potential overt bodily behavior (i.e., dispositions to overt bodily behavior). Logical behaviorism was much discussed from roughly the 1930s until the early 1960s. (While Ryle is sometimes counted as a logical behaviorist, he was not committed to the thesis that all mental talk can be translated into behavioral talk.) The translations promised by logical behaviorism appear unachievable. As Putnam and others pointed out, one can fake being in pain and one can be in pain and yet not behave or be disposed to behave as if one were in pain (e.g., one might be paralyzed or might be a “super-spartan”). Logical behaviorism faces similar difficulties in translating sentences about (what Russell called) propositional attitudes (i.e., beliefs that p, desires that p, hopes that p, intentions that p, and the like). Consider the following sample proposal (similar to one offered by Carnap): one believes that the cat is on the mat if and only if one is disposed to assent to ‘The cat is on the mat’. First, the proposed translation meets the condition of being purely behavioral only if assenting is understandable in purely behavioral terms. That is doubtful. The proposal also fails to provide a sufficient or a necessary condition: someone may assent to ‘The cat is on the mat’ and yet not believe the cat is on the mat (for the person may be trying to deceive); and a belief that the cat is on the mat will dispose one to assent to ‘The cat is on the mat’ only if one understands what is being asked, wants to indicate that one believes the cat is on the mat, and so on. But none of these conditions is required for believing that the cat is on the mat. Moreover, to invoke any of these mentalistic conditions defeats the attempt to provide a purely behavioral translation of the belief sentence. Although the project of translation has been abandoned, in recent years Dennett has defended a view in the spirit of logical behaviorism, intentional systems theory: belief-desire talk functions to characterize overall patterns of dispositions to overt behavior (in an environmental context) for the purposes of predicting overt behavior. The theory is sometimes characterized as supervenient behaviorism since it implies that whether an individual has beliefs, desires, intentions and the like supervenes on his dispositions to overt behavior: if two individuals are exactly alike in respect of their dispositions to overt behavior, the one has intentional states if and only if the other does. (This view allows, however, that the contents of an individual’s intentional states—what the individual believes, desires, etc.—may depend on environmental factors. So it is not committed to the supervemence of the contents of intentional states on dispositions to overt behavior. See the discussion of content externalism below.) One objection to this view, due to Ned Block, is that it would mistakenly count as an intentional agent a giant look-up table—“a Blockhead”—that has the same dispositions to peripheral behavior as a genuine intentional agent. (A look-up table is a simple mechanical device that looks up preprogrammed responses.) |
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Identity theories |
In the early 1950s, Herbert Feigl claimed that mental states are brain states. He pointed out that if mental properties or state types are merely nomologically correlated with physical properties or state types, the connecting laws would be “nomological danglers”: irreducible to physical laws, and thus additional fundamental laws. According to the identity theory, the connecting laws are not fundamental laws (and so not nomological danglers) since they can be explained by identifying the mental and physical properties in question. In the late 1950s and the early 1960s, the philosopher Smart and the psychologist U.T. Place defended the materialist view that sensations are identical with brain processes. Smart claimed that while mental terms differ in meaning from physical terms, scientific investigation reveals that they have the same referents as certain physical terms. (Compare the fact that while ‘the Morning Star’ and ‘the Evening Star’ differ in meaning empirical investigation reveals the same referent: Venus.) Smart and Place claimed that feeling pain, e.g., is some brain process, exactly which one to be determined by scientific investigation. Smart claimed that sensation talk is paraphraseable in topic-neutral terms; i.e., in terms that leave open whether sensational properties are mental or physical. ‘I have an orange afterimage’ is paraphraseable (roughly) as: ‘There is something going on like what is going on when I have my eyes open, am awake, and there is an orange illuminated in good light in front of me, i.e., when I really see an orange’. The description is topic-neutral since it leaves open whether what is going on is mental or physical. Smart maintained that scientific investigation reveals that what in fact meets the topic-neutral description is a brain process. He held that psychophysical identity statements such as ‘Pain is C-fiber firing’ are contingent, likening these to, e.g., ‘Lightning is electrical discharge’, which is contingent and knowable only through empirical investigation. |
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Central state materialism
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This brand of materialism was defended in the late 1960s and the early 1970s by Armstrong and others. On this view, mental states are states that are apt to produce a certain range of behavior. Central state materialists maintain that scientific investigation reveals that such states are states of the central nervous system, and thus that mental states are contingently identical with states of the central nervous system. Unlike logical behaviorism, central state materialism does not imply that mental sentences can be translated into physical sentences. Unlike both logical behaviorism and intentional systems theory, central state materialism implies that mental states are actual internal states with causal effects. And unlike Cartesian interactionism, it holds that psychophysical interaction is just physical causal interaction.
Some central state materialists held in addition that the mind is the brain. However, if the mind were the brain, every change in the brain would be a change in the mind; and that seems false: not every little brain change amounts to a change of mind. Indeed, the mind ceases to exist when brain death occurs, while the brain continues to exist. The moral that most materialists nowadays draw from such considerations is that the mind is not any physical substance, since it is not a substance of any sort. To have a mind is not to possess a special substance, but rather to have certain capacities—to think, feel, etc. To that extent, Ryle was right. However, central state materialists insist that the properly functioning brain is the material seat of mental capacities, that the exercise of mental capacities consists of brain processes, and that mental states are brain states that can produce behavior. Epistemological objections have been raised to identity theories. As self-conscious beings, we have a kind of privileged access to our own mental states. The exact avenue of privileged access, whether it is introspection or not, is controversial. But it has seemed to many philosophers that our access to our own mental states is privileged in being open only to us, whereas we lack any privileged access to the states of our central nervous systems. We come to know about central nervous system states in the same way we come to know about the central nervous system states of others. So, against central state materialism and the identity theory, it is claimed that mental states cannot be states of our central nervous systems. Taking privileged access to imply that we have incorrigible knowledge of our conscious mental states, and despairing of squaring privileged access so understood with materialism, Rorty advocated eliminative materialism, the thesis that there actually are no mental phenomena. A more common materialist response, however, is to deny that privileged access entails incorrigibility and to maintain that privileged access is compatible with materialism. Some materialists maintain that while certain types of mental states (e.g., sensations) are types of neurological states, it will be knowable only by empirical investigation that they are. Suppose pain is a neural state N. It will be only a posteriori knowable that pain is N. Via the avenue of privileged access, one comes to believe that one is in a pain state, but not that one is in an N-state. One can believe one is in a pain state without believing that one is in an N-state because the concept of pain is different from the concept of N. Nevertheless, pain is N. (Compare the fact that while water is H2O, the concept of water is different from that of H2O. Thus, while water is H2O, one can believe there is water in the glass without believing that there is H2O in it. The avenue of privileged access presents N conceptualized as pain, but never as neurological state N. The avenue of privileged access involves the exercise of mental, but not neurophysiological, concepts. However, our mental concepts answer to—apply in virtue of—the same properties (state types) as do certain of our neurophysiological concepts. The identity theory and central state materialism both hold that there are contingent psychophysical property and type identities. Some theorists in this tradition tried to distinguish a notion of theoretical identity from the notion of strict identity. They held that mental states are theoretically, but not strictly, identical with brain states. Against any such distinction, Kripke argued that identities are metaphysically necessary, i.e., hold in every possible world. If A = B, then necessarily A = B. Kripke acknowledged that there can be contingent statements of identity. But such statements, he argued, will employ at least one term that is not a rigid designator, i.e., a term that designates the same thing in every world in which it designates anything. Thus, since ‘the inventor of bifocals’ is a non-rigid designator, ‘Benjamin Franklin is the inventor of bifocals’ is contingent. While Franklin is the inventor of bifocals, he might not have been. However, statements of identity in which the identity sign is flanked by rigid designators are, if true, metaphysically necessary. Kripke held that proper names are rigid designators, and hence, the true identity statement ‘Cicero is Tully’ is metaphysically necessary. Nonetheless, a metaphysically necessary identity statement can be knowable only a posteriori. Indeed, ‘Cicero is Tully’ is knowable only a posteriori. Both ‘water’ and ‘H2O’, he maintained, are rigid designators: each designates the same kind of stuff in every possible world. And he thus maintained that it is metaphysically necessary that water is H2O, despite its not being a priori knowable that water is H2O. On Kripke’s view, any psychophysical identity statement that employs mental terms and physical terms that are rigid designators will also be metaphysically necessary, if true. Central state materialists maintain that mental concepts are equivalent to concepts whose descriptive content is the state that is apt to produce such-and-such behavior in such-and-such circumstances. These defining descriptions for mental concepts are intended to be meaning-giving, not contingent reference-fixing descriptions; they are, moreover, not rigid designators. Thus, the central state materialists can concede that all identities are necessary, but maintain that psychophysical claims of identity are contingent claims of identity since the mental terms that figure in those statements are not rigid designators. However, Kripke maintained that our concepts of sensations and other qualitative states are not equivalent to the sorts of descriptions in question. The term ‘pain’, he maintained, is a rigid designator. This position might be refuted by a successful functional analysis of the concept of pain in physical and/or topic-neutral terms. However, no successful analysis of this sort has yet been produced. (See the section on consciousness below.) A materialist can grant Kripke that ‘pain’ is a rigid designator and claim that a statement such as ‘Pain is C-fiber firing’ will be metaphysically necessary if true, but only a posteriori knowable. However, Kripke raised a formidable problem for this materialism. He pointed out that if a statement is metaphysically necessary but only a posteriori knowable, its appearance of contingency calls for explanation. Despite being metaphysically necessary, ‘Water is H2O’ appears contingent. According to Kripke, we explain this appearance by noting that one can coherently imagine a world in which something has all the phenomenal properties of water, and so is an “epistemic counterpart” of it, yet is not H2O. The fact that we can coherently imagine such epistemic counterparts explains why ‘Water is H2O’ appears contingent. But no such explanation is available for (e.g.) ‘Pain is C-fiber firing’. For an epistemic counterpart of pain, something with the phenomenal properties of pain—the feel of pain—is pain. Something can look, smell, taste, and feel like water yet not be water. But whatever feels like pain is pain: pain is a feeling. In contrast, we can explain the apparent contingency of claims like ‘Water is H2O’ because water is not constituted by its phenomenal properties; our concept of water allows that it may have a “hidden essence,” i.e., an essential microstructure. If Kripke is right, then anyone who maintains that a statement of identity concerning a type of bodily sensation and a type of physical state is metaphysically necessary yet a posteriori, must explain the appearance of contingency in a way that differs from the way Kripke explains the appearance of contingency of ‘Water is H2O’. This is a formidable challenge. (The final section, on consciousness, sketches some materialist responses to it.) The general issue of property and state type identity is controversial. The claim that water is H2O despite the fact that the concept of water is distinct from the concept of H2O seems plausible. However, property or state type identity is more controversial than the identity of types of substances. For properties or state types, there are no generally accepted “non-duplication principles” —to use a phrase of David Lewis’s. (A non-duplication principle for A’s will say that no two A’s can be exactly alike in a certain respect; e.g., no two sets can have exactly the same members.) It is widely denied, for instance, that no two properties can be possessed by exactly the same things. Two properties, it is claimed, can be possessed by the same things; likewise, two state types can occur in the same space-time regions. Even assuming that mental concepts are distinct from physical concepts, the issue of whether mental state types are physical state types raises the controversial issue of the non-duplication principle for state types. |
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Token and type physicalisms |
Token physicalism is the thesis that every particular is physical. Type physicalism is the thesis that every type or kind of entity is physical; thus, the identity thesis and central state materialism are type physicalist theses since they imply that types of mental states are types of physical states. Type physicalism implies token physicalism: given the former, every token falls under some physical type, and therefore is token-token identical with some token of a physical type. But token physicalism does not imply type physicalism; the former leaves open whether physical tokens fall under non-physical types. Some doctrines billed as materialist or physicalist embrace token epiphenomenalism, but reject type physicalism. |
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Non-reductive materialism |
This form of materialism implies token physicalism, but denies type physicalism and, as well, that mental types (properties, etc.) are reducible to physical types. This doctrine has been discussed since at least the late nineteenth century and was widely discussed in the first third of the twentieth century. The British philosophers George Henry Lewes, Samuel Alexander, Lloyd Morgan, and C.D. Broad all held or thought plausible a certain version of non-reductive materialism. They held or sympathized with the view that every substance either is or is wholly made up of physical particles, that the well-functioning brain is the material seat of mental capacities, and that token mental states (events, processes, etc.) are token neurophysiological states (events, processes, etc.). However, they either held or thought plausible the view that mental capacities, properties, etc., emerge from, and thus do not reduce to, physical capacities, properties, etc. Lewes coined the term ‘emergence’; and Broad later labeled the doctrine emergent materialism. Emergent materialists maintain that laws correlating mental and physical properties are irreducible. (These laws would be what Feigl called nomological danglers.) Emergentists maintain that, despite their untidiness, such laws must be accepted with natural piety. Davidson’s doctrine of anomalous monism is a current brand of non-reductive materialism. He explicitly formulates this materialist thesis for events; and his irreducibility thesis is restricted to intentional mental types—e.g., believings, desirings, and intendings. Anomalous monism says that every event token is physical, but that intentional mental predicates and concepts (ones expressing propositional attitudes) do not reduce, by law or definition, to physical predicates or concepts. Davidson offers an original argument for this irreducibility thesis. Mental predicates and concepts are, he claims, governed by constitutive principles of rationality, but physical predicates and concepts are not. This difference, he contends, excludes the possibility of reduction of mental predicates and concepts to physical ones. Davidson denies, moreover, that there are strict psychological or psychophysical laws. He calls the conjunction of this thesis and his irreducibility thesis the principle of the anomalism of the mental. His argument for token physicalism (for events) appeals to the principle of the anomalism of the mental and to the principle of the nomological character of causality: when two events are causally related, they are subsumed by a strict law. He maintains that all strict laws are physical. Given that claim, and given the principle of the nomological character of causality, it follows that every event that is a cause or effect is a physical event. On this view, psychophysical causation is just causation between physical events. Stephen Schiffer has also maintained a non-reductive materialism, one he calls ontological physicalism and sentential dualism: every particular is physical, but mental truths are irreducible to physical truths. Non-reductive materialism presupposes that mental state (event) tokens can fall under physical state types and, thereby, count as physical state tokens. This presupposition is controversial; no uncontroversial non-duplication principle for state tokens settles the issue. Suppose, however, that mental state tokens are physical state tokens, despite mental state types not being physical state types. The issue of how mental state types and physical state types are related remains. Suppose that some physical token x is of a mental type M (say, a belief that the cat is on the mat) and some other physical token y is not of type M. There must, it seems, be some difference between x and y in virtue of which x is, and y is not, of type M. Otherwise, it is simply a brute fact that x is and y is not of type M. That, however, seems implausible. The claim that certain physical state tokens fall under mental state types simply as a matter of brute fact would leave the difference in question utterly mysterious. But if it is not a brute fact, then there is some explanation of why a certain physical state is a mental state of a certain sort. The non-reductive materialist owes us an explanation that does not imply psychophysical reduction. Moreover, even though the non-reductive materialist can claim that mental states are causes because they are physical states with physical effects, there is some question whether mental state types are relevant to causal relations. Suppose every state is a physical state. Given that physical states causally interact in virtue of falling under physical types, it follows that whenever states causally interact they do so in virtue of falling under physical types. That raises the issue of whether states are ever causes in virtue of falling under mental types. Type epiphenomenalism is the thesis that no state can cause anything in virtue of falling under a mental type. Token epiphenomenalism, the thesis that no mental state can cause anything, implies type epiphenomenalism, but not conversely. Non-reductive materialists are not committed to token physicalism. However, token epiphenomenalism may be false but type epiphenomenalism true since mental states may be causes only in virtue of falling under physical types, never in virtue of falling under mental types. Broad raised the issue of type epiphenomenalism and discussed whether emergent materialism is committed to it. Ted Honderich, Jaegwon Kim, Ernest Sosa, and others have in recent years raised the issue of whether non-reductive materialism is committed to type epiphenomenalism. Brian McLaughlin has argued that the claim that an event acts as a cause in virtue of falling under a certain physical type is consistent with the claim that it also acts as a cause in virtue of falling under a certain mental type, even when the mental type is not identical with the physical type. But even if this is so, the relationship between mental types and physical types must be addressed. Ernest LePore and Barry Loewer, Frank Jackson and Philip Pettit, Stephen Yablo, and others have attempted to characterize a relation between mental types and physical types that allows for the causal relevance of mental types. But whether there is a relation between mental and physical properties that is both adequate to secure the causal relevance of mental properties and available to non-reductive materialists remains an open question. Davidson’s anomalous monism may appear to be a kind of dual-aspect theory: there are events and they can have two sorts of autonomous aspects, mental and physical. However, while Davidson holds that mental properties (or types) do not reduce to physical ones, he also holds that the mental properties of an event depend on its physical properties in that the former supervene on the latter in this sense: no two events can be exactly alike in every physical respect and yet differ in some mental respect. This proposal introduced the notion of supervenience into contem- porary philosophy of mind. Often non-reductive materialists argue that mental properties (types) supervene on physical properties (types). Kim, however, has distinguished various supervenience relations, and argues that some are too weak to count as versions of materialism (as opposed to, say, dual-aspect theory), while other supervenience relations are too strong to use to formulate non-reductive materialism since they imply reducibility. According to Kim, non-reductive materialism is an unstable position. |
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Materialism as a supervenience thesis |
Several philosophers have in recent years attempted to define the thesis of materialism using a global supervenience thesis. Their aim is not to formulate a brand of non-reductive materialism; they maintain that their supervenience thesis may well imply reducibility. Their aim is, rather, to formulate a thesis to which anyone who counts as a genuine materialist must subscribe. David Lewis has maintained that materialism is true if and only if any non-alien possible worlds that are physically indiscernible are mentally indiscernible as well. Non-alien possible worlds are worlds that have exactly the same perfectly natural properties as the actual world. Frank Jackson has offered this proposal: materialism is true if and only if any minimal physical duplicate of the actual world is a duplicate simpliciter of the actual world. A world is a physical duplicate of the actual world if and only if it is exactly like the actual world in every physical respect (physical particular for physical particular, physical property for physical property, physical relation for physical relation, etc.); and a world is a duplicate simpliciter of the actual world if and only if it is exactly like the actual world in every respect. A minimal physical duplicate of the actual world is a physical duplicate that contains nothing else (by way of particulars, kinds, properties, etc.) than it must in order to be a physical duplicate of the actual world. Two questions arise for any formulation of the thesis of materialism. Is it adequate to materialism? And, if it is, is it true? |
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Functionalism |
the view that what makes a state a realization of a mental state is its playing a certain causal role—remains a leading theory of mind. But functionalism faces formidable difficulties. Block has pinpointed one. On the one hand, if the input and output states that figure in the causal role alleged to define a certain mental state are specified in insufficient detail, the functional definition will be too liberal: it will mistakenly classify certain states as of that mental type. On the other hand, if the input and output states are specified in too much detail, the functional definition will be chauvinistic: it will fail to count certain states as instances of the mental state that are in fact such instances. Moreover, it has also been argued that functionalism cannot capture conscious states since types of conscious states do not admit of functional definitions. |
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Cognitive psychology |
Many claim that one aim of cognitive psychology is to provide explanations of intentional capacities, capacities to be in intentional states (e.g., believing) and to engage in intentional activities (e.g., reasoning). Fodor has argued that classical cognitive psychology postulates a cognitive architecture that includes a language of thought: a system of mental representation with a combinatorial syntax and semantics, and computational processes defined over these mental representations in virtue of their syntactic structures. On this view, cognition is rule-governed symbol manipulation. Mental symbols have meanings, but they participate in computational processes solely in virtue of their syntactic or formal properties. The mind is, so to speak, a syntactic engine. The view implies a kind of content parallelism: syntax-sensitive causal transitions between symbols will preserve semantic coherence. Fodor has maintained that, on this language-of-thought view of cognition (the classical view), being in a beliefthat-p state can be understood as consisting in bearing a computational relation (one that is constitutive of belief) to a sentence in the language of thought that means that p; and similarly for desire, intention, and the like. The explanation of intentional capacities will be provided by a computational theory for mental sentences in conjunction with a psychosemantic theory, a theory of meaning for mental sentences. A research program in cognitive science called connectionism postulates networks of neuron-like units. The units can be either on or off, or can have continuous levels of activation. Units are connected, the connections have various degrees of strength, and the connections can be either inhibitory or excitatory. Connectionism has provided fruitful models for studying how neural networks compute information. Moreover, connectionists have had much success in modeling pattern recognition tasks (e.g., facial recognition) and tasks consisting of learning categories from examples. Some connectionists maintain that connectionism will yield an alternative to the classical language-of-thought account of intentional states and capacities. However, some favor a mixed-models approach to cognition: some cognitive capacities are symbolic, some connectionist. And some hold that connectionism will yield an implementational architecture for a symbolic cognitive architecture, one that will help explain how a symbolic cognitive architecture is realized in the nervous system. |
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Content externalism |
Many today hold that Twin-Earth thought experiments by Putnam and Tyler Burge show that the contents of a subject’s mental states do not supervene on intrinsic properties of the subject: two individuals can be exactly alike in every intrinsic respect, yet be in mental states with different contents. (In response to Twin-Earth thought experiments, some philosophers have, however, attempted to characterize a notion of narrow content, a kind of content that supervenes on intrinsic properties of thinkers.) Content, externalists claim, depends on extrinsic-contextual factors. If externalism is correct, then a psychosemantic theory must examine the relation between mental symbols and the extrinsic, contextual factors that determine contents. Stephen Stich has argued that psychology should eschew psychosemantics and concern itself only with the syntactic properties of mental sentences. Such a psychology could not explain intentional capacities. But Stich urges that computational psychology also eschew that explanatory goal. If, however, psychology is to explain intentional capacities, a psychosemantic theory is needed. Dretske, Fodor, Ruth Millikan, and David Papineau have each independently attempted to provide, in physicalistically respectable terms, foundations for a naturalized externalist theory of the content of mental sentences or internal physical states. Perhaps the leading problem for these theories of content is to explain how the physical and functional facts about a state determine a unique content for it. Appealing to work by Quine and by Kripke, some philosophers argue that such facts will not determine unique contents. Both causal and epistemic concerns have been raised about externalist theories of content. Such theories invite the question whether the property of having a certain content is ever causally relevant. If content is a contextual property of a state that has it, can states have effects in virtue of their having a certain content? This is an important issue because intentional states figure in explanations not only in virtue of their intentional mode (whether they are beliefs, or desires, etc.) but also in virtue of their contents. Consider an everyday belief-desire explanation. The fact that the subject’s belief was that there was milk in the refrigerator and the fact that the subject’s desire was for milk are both essential to the belief and desire explaining why the subject went to the refrigerator. Dretske, who maintains that content depends on a causal-historical context, has attempted to explain how the property of having a certain content can be causally relevant even though the possession of the property depends on causal-historical factors. And various other philosophers have attempted to explain how the causal relevance of content can be squared with the fact that it fails to supervene on intrinsic properties of the subject. A further controversial question is whether externalism is consistent with our having privileged access to what we are thinking. |
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Consciousness |
Conscious states such as pain states, visual experiences, and so on, are such that it is “like” something for the subject of the state to be in them. Such states have a qualitative aspect, a phenomenological character. The what-it-is-like aspects of experiences are called qualia. Qualia pose a serious difficulty for physicalism. Broad argued that one can know all the physical properties of a chemical and how it causally interacts with other physical phenomena and yet not know what it is like to smell it. He concluded that the smell of the chemical is not itself a physical property, but rather an irreducible emergent property. Frank Jackson has recently defended a version of the argument, which has been dubbed the knowledge argument. Jackson argues that a super-scientist, Mary, who knows all the physical and functional facts about color vision, light, and matter, but has never experienced redness since she has spent her entire life in a black and white room, would not know what it is like to visually experience red. He concludes that the physical and functional (topic-neutral) facts do not entail all the facts, and thus materialism is false. In response, Lawrence Nemirow, David Lewis, and others have argued that knowing what it is like to be in a certain conscious state is, in part, a matter of know-how (e.g., to be able to imagine oneself in the state) rather than factual knowledge, and that the failure of knowledge of the physical and functional facts to yield such know-how does not imply the falsity of materialism. Functionalism seems unable to solve the problem of qualia since qualia seem not to be functionally definable. In the 1970s, Fodor and Ned Block argued that two states can have the same causal role, thereby realizing the same functional state, yet the qualia associated with each can be inverted. This is called the problem of inverted qualia. The color spectrum, e.g., might be inverted for two individuals (a possibility raised by Locke), despite their being in the same functional states. They further argued that two states might realize the same functional state, yet the one might have qualia associated with it and the other not. This is called the problem of absent qualia. Sydney Shoemaker has argued that the possibility of absent qualia can be ruled out on functionalist grounds. However, he has also refined the inverted qualia scenario and further articulated the problem it poses for functionalism. Whether functionalism or physicalism can avoid the problems of absent and inverted qualia remains an open question. Thomas Nagel claims that conscious states are subjective: to fully understand them, one must understand what it is like to be in them, but one can do that only by taking up the experiential point of view of a subject in them. Physical states, in contrast, are objective. Physical science attempts to characterize the world in abstraction from the experiential point of view of any subject. According to Nagel, whether phenomenal mental states reduce to physical states turns on whether subjective states reduce to objective states; and, at present, he claims, we have no understanding of how they could. Nagel has suggested that consciousness may be explainable only by appeal to as yet undiscovered basic non-mental, non-physical properties—“proto-mental properties”—the idea being that experiential points of view might be constituted by proto-mental properties together with physical properties. He thus claims that panphysicism is worthy of serious consideration. Frank Jackson, James Van Cleve, and David Chalmers have argued that conscious properties are emergent, i.e., fundamental, irreducible macro-properties; and Chalmers sympathizes with a brand of panphysicism. Colin McGinn claims that while conscious properties are likely reductively explainable by brain properties, our minds seem conceptually closed to the explaining properties: we are unable to conceptualize them, just as a cat is unable to conceptualize a square root. Dennett attempts to explain consciousness in supervenient behaviorist terms. David Rosenthal argues that consciousness is a special case of intentionality —more specifically, that conscious states are just states we can come in a certain direct way to believe we are in. Dretske, William Lycan, and Michael Tye argue that conscious properties are intentional properties and physicalistically reducible. Patricia Churchland argues that conscious phenomena are reducible to neurological phenomena. Brian Loar contends that qualia are identical with either functional or neurological states of the brain; and Christopher Hill argues specifically that qualia are identical with neurological states. Loar and Hill attempt to explain away the appearance of contingency of psychophysical identity claims, but in a way different from the way Kripke attempts to explain the appearance of contingency of ‘Water is H2O’, since they concede that that mode of explanation is unavailable. They appeal to differences in the conceptual roles of neurological and functional concepts by contrast with phenomenal concepts. They argue that while such concepts are different, they answer to the same properties. The nature of consciousness thus remains a matter of dispute. |
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Sartre, Jean-Paul (1905 - 1980) |
French philosopher and writer, the leading advocate of existentialism during the years following World War II. The heart of his philosophy was the precious notion of freedom and its concomitant sense of personal responsibility. He insisted, in an interview a few years before his death, that he never ceased to believe that “in the end one is always responsible for what is made of one,” only a slight revision of his earlier, bolder slogan, “man makes himself.” To be sure, as a student of Hegel, Marx, Husserl, and Heidegger—and because of his own physical frailty and the tragedies of the war—Sartre had to be well aware of the many constraints and obstacles to human freedom, but as a Cartesian, he never deviated from Descartes’s classical portrait of human consciousness as free and distinct from the physical universe it inhabits. One is never free of one’s “situation,” Sartre tells us, though one is always free to deny (“negate”) that situation and to try to change it. To be human, to be conscious, is to be free to imagine, free to choose, and responsible for one’s lot in life. As a student, Sartre was fascinated by Husserl’s new philosophical method, phenomenology. His first essays were direct responses to Husserl and applications of the phenomenological method. His essay on The Imagination in 1936 established the groundwork for much of what was to follow: the celebration of our remarkable freedom to imagine the world other than it is and (following Kant) the way that this ability informs all of our experience. In The Transcendence of the Ego (1937) he reconsidered Husserl’s central idea of a “phenomenological reduction” (the idea of examining the essential structures of consciousness as such) and argued (following Heidegger) that one cannot examine consciousness without at the same time recognizing the reality of actual objects in the world. In other words, there can be no such “reduction”. In his novel Nausea (1938), Sartre made this point in a protracted example: his bored and often nauseated narrator confronts a gnarled chestnut tree in the park and recognizes with a visceral shock that its presence is simply given and utterly irreducible. In The Transcendence of the Ego Sartre also reconsiders the notion of the self, which Husserl (and so many earlier philosophers) had identified with consciousness. But the self, Sartre argues, is not “in” consciousness, much less identical to it. The self is out there “in the world, like the self of another.” In other words, the self is an ongoing project in the world with other people; it is not simply self-awareness or self-consciousness as such (“I think, therefore I am”). This separation of self and consciousness and the rejection of the self as simply self-consciousness provide the framework for Sartre’s greatest philosophical treatise, L’être et le néant (Being and Nothingness, 1943). Its structure is unabashedly Cartesian, consciousness (“being-for-itself” or pour soi) on the one side, the existence of mere things (“being-in-itself” or en soi) on the other. (The phraseology comes from Hegel.) But Sartre does not fall into the Cartesian trap of dësignating these two types of being as separate “substances.” Instead, Sartre describes consciousness as “nothing’—“not a thing” but an activity, “a wind blowing from nowhere toward the world.” Sartre often resorts to visceral metaphors when developing this theme (e.g., “a worm coiled in the heart of being”), but much of what he is arguing is familiar to philosophical readers in the more metaphor-free work of Kant, who also warned against the follies (“paralogisms”) of understanding consciousness as itself a (possible) object of consciousness rather than as the activity of constituting the objects of consciousness. (As the lens of a camera can never see itself—and in a mirror only sees a reflection of itself—consciousness can never view itself as consciousness and is only aware of itself—“for itself”—through its experience of objects.) Ontologically, one might think of “nothingness” as “no-thing-ness,” a much less outrageous suggestion than those that would make it an odd sort of a thing. It is through the nothingness of consciousness and its activities that negation comes into the world, our ability to imagine the world other than it is and the inescapable necessity of imagining ourselves other than we seem to be. And because consciousness is nothingness, it is not subject to the rules of causality. Central to the argument of L’être et le néant and Sartre’s insistence on the primacy of human freedom is his insistence that consciousness cannot be understood in causal terms. It is always self-determining and, as such, “it always is what it is not, and is not what it is”—a playful paradox that refers to the fact that we are always in the process of choosing. Consciousness is “nothing,” but the self is always on its way to being something. Throughout our lives we accumulate a body of facts that are true of us—our “facticity”—but during our lives we remain free to envision new possibilities, to reform ourselves and to reinterpret our facticity in the light of new projects and ambitions—our “transcendence.” This indeterminacy means that we can never be anything, and when we try to establish ourselves as something particular - whether a social role (policeman, waiter) or a certain character (shy, intellectual, cowardly)—we are in “bad faith.” Bad faith is erroneously viewing ourselves as something fixed and settled (Sartre utterly rejects Freud and his theory of the unconscious determination of our personalities and behavior), but it is also bad faith to view oneself as a being of infinite possibilities and ignore the always restrictive facts and circumstances within which all choices must be made. On the one hand, we are always trying to define ourselves; on the other hand we are always free to break away from what we are, and always responsible for what we have made of ourselves. But there is no easy resolution or “balance” between facticity and freedom, rather a kind of dialectic or tension. The result is our frustrated desire to be God, to be both in-itself and for-itself. But this is not so much blasphemy as an expression of despair, a form of ontological original sin, the impossibility of being both free and what we want to be. Life for Sartre is yet more complicated. There is a third basic ontological category, on a par with the being-in-itself and being-for-itself and not derivative of them. He calls it “being-for-others.” To say that it is not derivative is to insist that our knowledge of others is not inferred, e.g. by some argument by analogy, from the behavior of others, and we ourselves are not wholly constituted by our self-determinations and the facts about us. Sartre gives us a brutal but familiar everyday example of our experience of being-for-others in what he calls “the look” (le regard). Someone catches us “in the act” of doing something humiliating, and we find ourselves defining ourselves (probably also resisting that definition) in their terms. In his Saint Genet (1953), Sartre describes such a conversion of the ten-year-old Jean Genet into a thief. So, too, we tend to “catch” one another in the judgments we make and define one another in terms that are often unflattering. But these judgments become an essential and ineluctible ingredient in our sense of ourselves, and they too lead to conflicts indeed, conflicts so basic and so frustrating that in his play Huis clos (No Exit, 1943) Sartre has one of his characters utter the famous line, “Hell is other people.” In his later works, notably his Critique of Dialectical Reason (1958-59), Sartre turned in increasingly to politics and, in particular, toward a defense of Marxism on existentialist principles. This entailed rejecting materialist determinism, but it also required a new sense of solidarity (or what Sartre had wistfully called, following Heidegger, Mitsein or “being with others”). Thus in his later work he struggled to find a way of overcoming the conflict and insularity or the rather “bourgeois” consciousness he had described in Being and Nothingness. Not surprisingly (given his constant political activities) he found it in revolutionary engagement. Consonant with his rejection of bourgeois selfhood, Sartre turned down the 1964 Nobel prize for literature. |
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existentialism
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A philosophical and literary movement that came to prominence in Europe, particularly in France, immediately after World War II, and that focused on the uniqueness of each human individual as distinguished from abstract universal human qualities. Historians differ as to antecedents. Some see an existentialist precursor in Pascal, whose aphoristically expressed Catholic fideism questioned the power of rationalist thought and preferred the God of Scripture to the abstract “God of the philosophers.” Many agree that Kierkegaard, whose fundamentally similar but Protestant fideism was based on a profound unwillingness to situate either God or any individual’s relationship with God within a systematic philosophy, as Hegel had done, should be considered the first modern existentialist, though he too lived long before the term emerged. Others find a proto-existentialist in Nietzsche, because of the aphoristic and anti-systematic nature of his writings, and on the literary side, in Dostoevsky. (A number of twentieth-century novelists, such as Franz Kafka, have been labeled existentialists.) A strong existentialist strain is to be found in certain other theist philosophers who have written since Kierkegaard, such as Lequier, Berdyaev, Marcel, Jaspers, and Buber, but Marcel later decided to reject the label ‘existentialist’, which he had previously employed. This reflects its increasing identification with the atheistic existentialism of Sartre, whose successes, as in the novel Nausea, and the philosophical work Being and Nothingness, did most to popularize the word. A mass-audience lecture, “Existentialism Is a Humanism,” which Sartre (to his later regret) allowed to be published, provided the occasion for Heidegger, whose early thought had greatly influenced Sartre’s evolution, to take his distance from Sartre’s existentialism, in particular for its self-conscious concentration on human reality over Being. Heidegger’s Letter on Humanism, written in reply to a French admirer, signals an important turn in his thinking. Nevertheless, many historians continue to classify Heidegger as an existentialist—quite reasonably, given his early emphasis on existential categories and ideas such as anxiety in the presence of death, our sense of being “thrown” into existence, and our temptation to choose anonymity over authenticity in our conduct. This illustrates the difficulty of fixing the term ‘existentialism’. Other French thinkers of the time, all acquaintances of Sartre’s, who are often classified as existentialists, are Camus, Simone de Beauvoir, and, though with less reason, Merleau-Ponty. Camus’s novels, such as The Stranger and The Plague, are cited along with Nausea as epitomizing the uniqueness of the existentialist antihero who acts out of authenticity, i.e., in freedom from any conventional expectations about what so-called human nature (a concept rejected by Sartre) supposedly requires in a given situation, and with a sense of personal responsibility and absolute lucidity that precludes the “bad faith” or lying to oneself that characterizes most conventional human behavior. Good scholarship prescribes caution, however, about superimposing too many Sartrean categories on Camus. In fact the latter, in his brief philosophical essays, notably The Myth of Sisyphus, distinguishes existentialist writers and philosophers, such as Kierkegaard, from absurdist thinkers and heroes, whom he regards more highly, and of whom the mythical Sisyphus (condemned eternally by the gods to roll a huge boulder up a hill before being forced, just before reaching the summit, to start anew) is the epitome. Camus focuses on the concept of the absurd, which Kierkegaard had used to characterize the object of his religious faith (an incarnate God). But for Camus existential absurdity lies in the fact, as he sees it, that there is always at best an imperfect fit between human reasoning and its intended objects, hence an impossibility of achieving certitude. Kierkegaard’s leap of faith is, for Camus, one more pseudo-solution to this hard, absurdist reality. Almost alone among those named besides Sartre (who himself concentrated more on social and political thought and became indebted to Marxism in his later years), Simone de Beauvoir (1908-86) unqualifiedly accepted the existentialist label. In The Ethics of Ambiguity, she attempted, using categories familiar in Sartre, to produce an existentialist ethics based on the recognition of radical human freedom as “projected”toward an open future, the rejection of inauthenticity, and a condemnation of the “spirit of seriousness” (akin to the “spirit of gravity”criticized by Nietzsche) whereby individuals identify themselves wholly with certain fixed qualities, values, tenets, or prejudices. Her feminist masterpiece, The Second Sex, relies heavily on the distinction, part existentialist and part Hegelian in inspiration, between a life of immanence, or passive acceptance of the role into which one has been socialized, and one of transcendence, actively and freely testing one’s possibilities with a view to redefining one’s future. Historically, women have been consigned to the sphere of immanence, says de Beauvoir, but in fact a woman in the traditional sense is not something that one is made, without appeal, but rather something that one becomes. The Sartrean ontology of Being and Nothingness, according to which there are two fundamental asymmetrical “regions of being,” being-in-itself and being-for-itself, the latter having no definable essence and hence, as “nothing” in itself, serving as the ground for freedom, creativity, and action, serves well as a theoretical framework for an existentialist approach to human existence. (Being and Nothingness also names a third ontological region, being-for-others, but that may be disregarded here.) However, it would be a mistake to treat even Sartre’s existentialist insights, much less those of others, as dependent on this ontology, to which he himself made little direct reference in his later works. Rather, it is the implications of the common central claim that we human beings exist without justification (hence “absurdly”) in a world into which we are “thrown,” condemned to assume full responsibility for our free actions and for the very values according to which we act, that make existentialism a continuing philosophical challenge, particularly to ethicists who believe right choices to be dictated by our alleged human essence or nature. |
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evidentialism |
In the philosophy of religion, the view that religious beliefs can be rationally accepted only if they are supported by one’s “total evidence,” understood to mean all the other propositions one knows or justifiably believes to be true. Evidentialists typically add that, in order to be rational, one’s degree of belief should be proportioned to the strength of the evidential support. Evidentialism was formulated by Locke as a weapon against the sectarians of his day and has since been used by Clifford (among many others) to attack religious belief in general. A milder form of evidentialism is found in Aquinas, who, unlike Clifford, thinks religion can meet the evidentialist challenge. A contrasting view is fideism, best understood as the claim that one’s fundamental religious convictions are not subject to independent rational assessment. A reason often given for this is that devotion to God should be one’s “ultimate concern,” and to subject faith to the judgment of reason is to place reason above God and make of it an idol. Proponents of fideism include Tertullian, Kierkegaard, Karl Barth, and some Wittgensteinians. A third view, which as yet lacks a generally accepted label, may be termed experientialism; it asserts that some religious beliefs are directly justified by religious experience. Experientialism differs from evidentialism in holding that religious beliefs can be rational without being supported by inferences from other beliefs one holds; thus theistic arguments are superfluous, whether or not there are any sound ones available. But experientialism is not fideism; it holds that religious beliefs may be directly grounded in religious experience without the mediation of other beliefs, and may be rationally warranted on that account, just as perceptual beliefs are directly grounded in perceptual experience. Recent examples of experientialism are found in Plantinga’s “Reformed Epistemology,” which asserts that religious beliefs grounded in experience can be “properly basic,” and in the contention of Alston that in religious experience the subject may be “perceiving God.” |
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Marx, Karl (1818 - 1883) |
German social philosopher, economic theorist, and revolutionary. He lived and worked as a journalist in Cologne, Paris, and Brussels. After the unsuccessful 1848 revolutions in Europe, he settled in London, doing research and writing and earning some money as correspondent for the New York Tribune. In early writings, he articulated his critique of the religiously and politically conservative implications of the then-reigning philosophy of Hegel, finding there an acceptance of existing private property relationships and of the alienation generated by them. Marx understood alienation as a state of radical disharmony (1) among individuals, (2) between them and their own life activity, or labor, and (3) between individuals and their system of production. Later, in his masterwork Capital (1867, 1885, 1894), Marx employed Hegel’s method of dialectic to generate an internal critique of the theory and practice of capitalism, showing that, under assumptions (notably that human labor is the source of economic value) found in such earlier theorists as Adam Smith, this system must undergo increasingly severe crises, resulting in the eventual seizure of control of the increasingly centralized means of production (factories, large farms, etc.) from the relatively small class of capitalist proprietors by the previously impoverished non-owners (the proletariat) in the interest of a thenceforth classless society. Marx’s early writings, somewhat utopian in tone, most never published during his lifetime, emphasize social ethics and ontology. In them, he characterizes his position as a “humanism” and a “naturalism.” In the Theses on Feuerbach, he charts a middle path between Hegel’s idealist account of the nature of history as the self-unfolding of spirit and what Marx regards as the ahistorical, mechanistic, and passive materialist philosophy of Feuerbach; Marx proposes a conception of history as forged by human activity, or praxis, within determinate material conditions that vary by time and place. In later Marxism, this general position is often labeled dialectical materialism. Marx began radically to question the nature of philosophy, coming to view it as ideology, i.e., a thought system parading as autonomous but in fact dependent on the material conditions of the society in which it is produced. The tone of Capital is therefore on the whole less philosophical and moralistic, more social scientific and tending toward historical determinism, than that of the earlier writings, but punctuated by bursts of indignation against the baneful effects of capitalism’s profit orientation and references to the “society of associated producers” (socialism or communism) that would, or could, replace capitalist society. His enthusiastic predictions of immanent worldwide revolutionary changes, in various letters, articles, and the famous Communist Manifesto (1848; jointly authored with his close collaborator, Friedrich Engels), depart from the generally more hypothetical character of the text of Capital itself. The linchpin that perhaps best connects Marx’s earlier and later thought and guarantees his enduring relevance as a social philosopher is his analysis of the role of human labor power as a peculiar type of commodity within a system of commodity exchange (his theory of surplus value). Labor’s peculiarity, according to him, lies in its capacity actively to generate more exchange value than it itself costs employers as subsistence wages. But to treat human beings as profit-generating commodities risks neglecting to treat them as human beings. |
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Marxism
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The philosophy of Karl Marx, or any of several systems of thought or approaches to social criticism derived from Marx. The term is also applied, incorrectly, to certain sociopolitical structures created by dominant Communist parties during the mid-twentieth century. Karl Marx himself, apprised of the ideas of certain French critics who invoked his name, remarked that he knew at least that he was not a Marxist. The fact that his collaborator, Friedrich Engels, a popularizer with a greater interest than Marx in the natural sciences, outlived him and wrote, among other things, a “dialectics of nature” that purported to discover certain universal natural laws, added to the confusion. Lenin, the leading Russian Communist revolutionary, near the end of his life discovered previously unacknowledged connections between Marx’s Capital (1867) and Hegel’s Science of Logic (1812-16) and concluded (in his Philosophical Notebooks) that Marxists for a half-century had not understood Marx. Specific political agendas of, among others, the Marxist faction within the turn-of-the-century German Social Democratic Party, the Bolshevik faction of Russian socialists led by Lenin, and later governments and parties claiming allegiance to “Marxist-Leninist principles” have contributed to reinterpretations. For several decades in the Soviet Union and countries allied with it, a broad agreement concerning fundamental Marxist doctrines was established and politically enforced, resulting in a doctrinaire version labeled “orthodox Marxism” and virtually ensuring the widespread, wholesale rejection of Marxism as such when dissidents taught to accept this version as authentic Marxism came to power. Marx never wrote a systematic exposition of his thought, which in any case drastically changed emphases across time and included elements of history, economics, and sociology as well as more traditional philosophical concerns. In one letter he specifically warns against regarding his historical account of Western capitalism as a transcendental analysis of the supposedly necessary historical development of any and all societies at a certain time. It is thus somewhat paradoxical that Marxism is often identified as a “totalizing” if not “totalitarian” system by post-modernist philosophers who reject global theories or “grand narratives” as inherently invalid. However, the evolution of Marxism since Marx’s time helps explain this identification. That “orthodox” Marxism would place heavy emphasis on historical determinism—the inevitability of a certain general sequence of events leading to the replacement of capitalism by a socialist economic system (in which, according to a formula in Marx’s Critique of the Gotha Program, each person would be remunerated according to his/her work) and eventually by a communist one (remuneration in accordance with individual needs)—was foreshadowed by Plekhanov. In The Role of the Individual in History, he portrayed individual idiosyncrasies as accidental: e.g., had Napoleon not existed the general course of history would not have turned out differently. In Materialism and Empiriocriticism, Lenin offered epistemological reinforcement for the notion that Marxism is the uniquely true worldview by defending a “copy” or “reflection” theory of knowledge according to which true concepts simply mirror objective reality, like photographs. Elsewhere, however, he argued against “economism, ” the inference that the historical inevitability of communism’s victory obviated political activism. Lenin instead maintained that, at least under the repressive political conditions of czarist Russia, only a clandestine party of professional revolutionaries, acting as the vanguard of the working class and in its interests, could produce fundamental change. Later, during the long political reign of Josef Stalin, the hegemonic Communist Party of the USSR was identified as the supreme interpreter of these interests, thus justifying totalitarian rule. So-called Western Marxism opposed this “orthodox” version, although the writings of one of its foremost early representatives, Georg Lukacs, who brilliantly perceived the close connection between Hegel’s philosophy and the early thought of Marx before the unpublished manuscripts proving this connection had been retrieved from archives, actually tended to reinforce both the view that the party incarnated the ideal interests of the proletariat (see his History and Class Consciousness) and an aesthetics favoring the art of “socialist realism” over more experimental forms. His contemporary, Karl Korsch, in Marxism as Philosophy, instead saw Marxism as above all a heuristic method, pointing to salient phenomena (e.g., social class, material conditioning) generally neglected by other philosophies. His counsel was in effect followed by the Frankfurt School of critical theory, including Walter Benjamin in the area of aesthetics, Theodor Adorno in social criticism, and Wilhelm Reich in psychology. A spate of “new Marxisms”—the relative degrees of their fidelity to Marx’s original thought cannot be weighed here—developed, especially in the wake of the gradual rediscovery of Marx’s more ethically oriented, less deterministic early writings. Among the names meriting special mention in this context are Ernst Bloch, who explored Marxism’s connection with utopian thinking; Herbert Marcuse, critic of the “one-dimensionality” of industrial society; the Praxis school (after the name of their journal and in view of their concern with analyzing social practices) of Yugoslav philosophers; and the later Jean-Paul Sartre. Also worthy of note are the writings, many of them composed in prison under Mussolini’s Italian Fascist rule, of Antonio Gramsci, who stressed the role of cultural factors in determining what is dominant politically and ideologically at any given time. Simultaneous with the decline and fall of regimes in which “orthodox Marxism” was officially privileged has been the recent development of new approaches, loosely connected by virtue of their utilization of techniques favored by British and American philosophers, collectively known as analytic Marxism. Problems of justice, theories of history, and the questionable nature of Marx’s theory of surplus value have been special concerns to these writers. This development suggests that the current unfashionableness of Marxism in many circles, due largely to its understandable but misleading identification with the aforementioned regimes, is itself only a temporary phenomenon, even if future Marxisms are likely to range even further from Marx’s own specific concerns while still sharing his commitment to identifying, explaining, and criticizing hierarchies of dominance and subordination, particularly those of an economic order, in human society. |
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praxis |
(from Greek prasso, ‘doing’, ‘acting’) In Aristotle, the sphere of thought and action that comprises the ethical and political life of man, contrasted with the theoretical designs of logic and epistemology (theoria). It was thus that ‘praxis’ acquired its general definition of ‘practice’ through a contrastive comparison with ‘theory’ Throughout the history of Western philosophy the concept of praxis found a place in a variety of philosophical vocabularies. Marx and the neo-Marxists linked the concept with a production paradigm in the interests of historical explanation. Within such a scheme of things the activities constituting the relations of production and exchange are seen as the dominant features of the socioeconomic history of humankind. Significations of ‘praxis’ are also discernible in the root meaning of pragma (deed, affair), which informed the development of American pragmatism. In more recent times the notion of praxis has played a prominent role in the formation of the school of critical theory, in which the performatives of praxis are seen to be more directly associated with the entwined phenomena of discourse, communication, and social practices The central philosophical issues addressed in the current literature on praxis have to do with the theory-practice relationship and the problems associated with a value-free science. The general thrust is that of undermining or subverting the traditional bifurcation of theory and practice via a recognition of praxis-oriented endeavors that antedate both theory construction and the construal of practice as a mere application of theory. Both the project of “pure theory,” which makes claims for a value-neutral standpoint, and the purely instrumentalist understanding of practice, as itself shorn of discernment and insight, are jettisoned. The consequent philosophical task becomes that of understanding human thought and action against the backdrop of the everyday communicative endeavors, habits, and skills, and social practices that make up our inheritance in the world. |
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critical theory |
Any social theory that is at the same time explanatory, normative, practical, and self-reflexive. The term was first developed by Horkheimer as a self-description of the Frankfurt School and its revision of Marxism. It now has a wider significance to include any critical, theoretical approach, including feminism and liberation philosophy. When they make claims to be scientific, such approaches attempt to give rigorous explanations of the causes of oppression, such as ideological beliefs or economic dependence; these explanations must in turn be verified by empirical evidence and employ the best available social and economic theories. Such explanations are also normative and critical, since they imply negative evaluations of current social practices. The explanations are also practical, in that they provide a better self-understanding for agents who may want to improve the social conditions that the theory negatively evaluates. Such change generally aims at “emancipation,” and theoretical insight empowers agents to remove limits to human freedom and the causes of human suffering. Finally, these theories must also be self-reflexive: they must account for their own conditions of possibility and for their potentially transformative effects. These requirements contradict the standard account of scientific theories and explanations, particularly positivism and its separation of fact and value. For this reason, the methodological writings of critical theorists often attack positivism and empiricism and attempt to construct alternative epistemologies. Critical theorists also reject relativism, since the cultural relativity of norms would undermine the basis of critical evaluation of social practices and emancipatory change. The difference between critical and non-critical theories can be illustrated by contrasting the Marxian and Mannheimian theories of ideology. Whereas Mannheim’s theory merely describes relations between ideas of social conditions, Marx’s theory tries to show how certain social practices require false beliefs about them by their participants. Marx’s theory not only explains why this is so, it also negatively evaluates those practices; it is practical in that by disillusioning participants, it makes them capable of transformative action. It is also self-reflexive, since it shows why some practices require illusions and others do not, and also why social crises and conflicts will lead agents to change their circumstances. It is scientific, in that it appeals to historical evidence and can be revised in light of better theories of social action, language, and rationality. Marx also claimed that his theory was superior for its special “dialectical method,” but this is now disputed by most critical theorists, who incorporate many different theories and methods. This broader definition of critical theory, however, leaves a gap between theory and practice and places an extra burden on critics to justify their critical theories without appeal to such notions as inevitable historcial progress. This problem has made critical theories more philosophical and concerned with questions of justification. |
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verificationism |
A metaphysical theory about what determines meaning: the meaning of a statement consists in its method(s) of verification. Verificationism thus differs radically from the account that identifies meaning with truth conditions, as is implicit in Frege’s work and explicit in Wittgenstein’s Tractatus and throughout the writings of Davidson. On Davidson’s theory, e.g., the crucial notions for a theory of meaning are truth and falsity. Contemporary verificationists, under the influence of the Oxford philosopher Michael Dummett, propose what they see as a constraint on the concept of truth rather than a criterion of meaningfulness. No foundational place is generally assigned in modern verificationist semantics to corroboration by observation statements; and modern verificationism is not reductionist. Thus, many philosophers read Quine’s “Two Dogmas of Empiricism” as rejecting verificationism. This is because they fail to notice an important distinction. What Quine rejects is not verificationism but “reductionism,” namely, the theory that there is, for each statement, a corresponding range of verifying conditions determinable a priori. Reductionism is inherently localist with regard to verification; whereas verificationism, as such, is neutral on whether verification is holistic. And, lastly, modern verificationism is, whereas traditional verificationism never was, connected with revisionism in the philosophy of logic and mathematics (e.g., rejecting the principle of bivalence). |
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phenomenology |
In the twentieth century, the philosophy developed by Husserl and some of his followers. The term has been used since the mid-eighteenth century and received a carefully defined technical meaning in the works of both Kant and Hegel, but it is not now used to refer to a homogeneous and systematically developed philosophical position. The question of what phenomenology is may suggest that phenomenology is one among the many contemporary philosophical conceptions that have a clearly delineated body of doctrines and whose essential characteristics can be expressed by a set of well-chosen statements. This notion is not correct, however. In contemporary philosophy there is no system or school called “phenomenology,” characterized by a clearly defined body of teachings. Phenomenology is neither a school nor a trend in contemporary philosophy. It is rather a movements whose proponents, for various reasons, have propelled it in many distinct directions, with the result that today it means different things to different people. While within the phenomenological movement as a whole there are several related currents, they, too, are by no means homogeneous. Though these currents have a common point of departure, they do not project toward the same destination. The thinking of most phenomenologists has changed so greatly that their respective views can be presented adequately only by showing them in their gradual development. This is true not only for Husserl, founder of the phenomenological movement, but also for such later phenomenologists as Scheler, N. Hartmann, Heidegger, Sartre, and Merleau-Ponty. To anyone who studies the phenomenological movement without prejudice the differences among its many currents are obvious. It has been said that phenomenology consists in an analysis and description of consciousness; it has been claimed also that phenomenology simply blends with existentialism. Phenomenology is indeed the study of essences, but it also attempts to place essences back into existence. It is a transcendental philosophy interested only in what is “left behind” after the phenomenological reduction is performed, but it also considers the world to be already there before reflection begins. For some philosophers phenomenology is speculation on transcendental subjectivity, whereas for others it is a method for approaching concrete existence. Some use phenomenology as a search for philosophy that accounts for space, time, and the world, just as we experience and “live” them. Finally, it has been said that phenomenology is an attempt to give a direct description of our experience as it is in itself without taking into account its psychological origin and its causal explanation; but Husserl speaks of a “genetic” as well as a “constitutive” phenomenology. To some people, finding such an abundance of ideas about one and the same subject constitutes a strange situation; for others it is annoying to contemplate the “confusion”; and there will be those who conclude that a philosophy that cannot define its own scope does not deserve the discussion that has been carried on in its regard. In the opinion of many, not only is this latter attitude not justified, but precisely the opposite view defended by Thevenaz should be adopted. As the term ‘phenomenology’ signifies first and foremost a methodical conception, Thevenaz argues that because this method, originally developed for a very particular and limited end, has been able to branch out in so many varying forms, it manifests a latent truth and power of renewal that implies an exceptional fecundity. Speaking of the great variety of conceptions within the phenomenological movement, Merleau-Ponty remarked that the responsible philosopher must recognize that phenomenology may be practiced and identified as a manner or a style of thinking, and that it existed as a movement before arriving at a complete awareness of itself as a philosophy. Rather than force a living movement into a system, then, it seems more in keeping with the ideal of the historian as well as the philosopher to follow the movement in its development, and attempt to describe and evaluate the many branches in and through which it has unfolded itself. In reality the picture is not as dark as it may seem at first sight. Notwithstanding the obvious differences, most phenomenologists share certain insights that are very important for their mutual philosophical conception as a whole. In this connection the following must be mentioned: (1) Most phenomenologists admit a radical difference between the “natural” and the “philosophical” attitude. This leads necessarily to an equally radical difference between philosophy and science. In characterizing this difference some phenomenologists, in agreement with Husserl, stress only epistemological issues, whereas others, in agreement with Heidegger, focus their attention exclusively on ontological topics. (2) Notwithstanding this radical difference, there is a complicated set of relationships between philosophy and science. Within the context of these relationships philosophy has in some sense a foundational task with respect to the sciences, whereas science offers to philosophy at least a substantial part of its philosophical problematic. (3) to achieve its task philosophy mist perform a certain reduction, or epoche, a radical change of attitude by which the philosopher turns things to their meanings, from the ontic to the ontological, from the realm of the objectified meaning as found in the sciences to the realm of meaning as immediately experienced in the “life-world.” In other words, although it remains true that the various phenomenologists differ in characterizing the reduction, no one seriously doubts its necessity. (4) All phenomenologists subscribe to the doctrine of intentionality, though most elaborate this doctrine in their own way. For Husserl intentionality is a characteristic of conscious phenomena or acts; in a deeper sense, it is the characteristic of a finite consciousness that originally finds itself without a world. For Heidegger and most existentialists it is the human reality itself that is intentional; as Being-in-the-world its essence consists in its ek-sistence, i.e. in its standing out toward the world. (5) All phenomenologists agree on the fundamental idea that the basic concern of philosophy is to answer the question concerning the “meaning and Being” of beings. All agree in addition that in trying to materialize this goal the philosopher should primarily be interested not in the ultimate cause of all finite beings, but in how the Being of beings and the Being of the world are to be constituted. Finally, all agree that in answering the question concerning the meaning of Being a privileged position is to be attributed to subjectivity, i.e., to that being which questions the Being of beings. Phenomenologists differ, however, the moment they have to specify what is meant by subjectivity. As noted above, whereas Husserl conceives it as a worldless monad, Heidegger and most later phenomenologists conceive it as being-in-the-world. Referring to Heidegger’s reinterpretation of his phenomenology, Husserl writes: one misinterprets my phenomenology backwards from a level which it was its very purpose to overcome, in other words, one has failed to understand the fundamental novelty of the phenomenological reduction and hence the progress from mundane subjectivity (i.e., man) to transcendental subjectivity; consequently one has remained stuck in an anthropology… which according to my doctrine has not yet reached the genuine philosophical level, and whose interpretation as philosophy means a lapse into “transcendental anthropologism, ” that is, “psychologism.” (6) All phenomenologists defend a certain form of intuitionism and subscribe to what Husserl calls the “principle of all principles”: “whatever presents itself in ‘intuition’ in primordial form (as it were in its bodily reality), is simply to be accepted as it gives itself out to be, though only within the limits in which it then presents itself.” Here again, however, each phenomenologist interprets this principle in keeping with his general conception of phenomenology as a whole. Thus, while phenomenologists do share certain insights, the development of the movement has nevertheless been such that it is not possible to give a simple definition of what phenomenology is. The fact remains that there are many phenomenologists and many phenomenologies. Therefore, one can only faithfully report what one has experienced of phenomenology by reading the phenomenologists. |
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phenomenalism |
The view that propositions asserting the existence of physical objects are equivalent in meaning to propositions asserting that subjects would have certain sequences of sensations were they to have certain others. The basic idea behind phenomenalism is compatible with a number of different analyses of the self or conscious subject. A phenomenalist might understand the self as a substance, a particular, or a construct out of actual and possible experience. The view also is compatible with any number of different analyses of the visual, tactile, auditory, olfactory, gustatory, and kinesthetic sensations described in the antecedents and consequents of the subjunctive conditionals that the phenomenalist uses to analyze physical object propositions (as illustrated in the last paragraph). Probably the most common analysis of sensations adopted by traditional phenomenalists is a sense-datum theory, with the sense-data construed as mind-dependent entities. But there is nothing to prevent a phenomenalist from accepting an adverbial theory or theory of appearing instead. The origins of phenomenalism are difficult to trace, in part because early statements of the view were usually not careful. In his Dialogues, Berkeley hinted at phenomenalism when he had Philonous explain how he could reconcile an ontology containing only minds and ideas with the story of a creation that took place before the existence of people. Philonous imagines that if he had been present at the creation he should have seen things, i.e., had sensations, in the order described in the Bible. It can also be argued, however, that J.S. Mill in An Examination of Sir William Hamilton’s Philosophy was the first to put forth a clearly phenomenalistic analysis when he identified matter with the “permanent possibility of sensation.” When Mill explained what these permanent possibilities are, he typically used conditionals that describe the sensations one would have if one were placed in certain conditions. The attraction of classical phenomenalism grew with the rise of logical positivism and its acceptance of the verifiability criterion of meaning. Phenomenalists were usually foundationalists who were convinced that justified belief in the physical world rested ultimately on our non-inferentially justified beliefs about our sensations. Implicitly committed to the view that only deductive and inductive inferences are legitimate, and further assuming that to be justified in believing one proposition P on the basis of another E, one must be justified in believing both E and that E makes P probable, the phenomenalist saw an insuperable difficulty in justifying belief in ordinary statements about the physical world given prevalent conceptions of physical objects. If all we ultimately have as our evidence for believing in physical objects is what we know about the occurrence of sensation, how can we establish sensation as evidence for the existence of physical objects? We obviously cannot deduce the existence of physical objects from any finite sequence of sensations. The sensations could, e.g., be hallucinatory. Nor, it seems, can we observe a correlation between sensation and something else in order to generate the premises of an inductive argument for the conclusion that sensations are reliable indicators of physical objects. The key to solving this problem, the phenomenalist argues, is to reduce assertions about the physical world to complicated assertions about the sequences of sensations a subject would have were he to have certain others. The truth of such conditionals, e.g., that if I have the clear visual impression of a cat, then there is one before me, might be mind-independent in the way in which one wants the truth of assertions about the physical world to be mind-independent. And to the phenomenalist’s great relief, it would seem that we could justify our belief in such conditional statements without having to correlate anything but sensations. Many philosophers today reject some of the epistemological, ontological, and metaphilosophical presuppositions with which phenomenalists approached the problem of understanding our relation to the physical world through sensation. But the argument that was historically most decisive in convincing many philosophers to abandon phenomenalism was the argument from perceptual relativity first advanced by Chisholm in “The Problem of Perception.” Chisholm offers a strategy for attacking any phenomenalistic analysis. The first move is to force the phenomenalist to state a conditional describing only sensations that is an alleged consequence of a physical object proposition. C.I. Lewis, e.g., in An Analysis of Knowledge and Valuation, claims that the assertion (P) that there is a doorknob before me and to the left entails (C) that if I were to seem to see a doorknob and seem to reach out and touch it then I would seem to feel it. Chisholm argues that if P really did entail C then there could be no assertion R that when conjoined with P did not entail C. There is, however, such an assertion: I am unable to move my limbs and my hands but am subject to delusions such that I think I am moving them; I often seem to be initiating a grasping motion but with no feeling of contacting anything. Chisholm argues, in effect, that what sensations one would have if one were to have certain others always depends in part on the internal and external physical conditions of perception and that this fact dooms any attempt to find necessary and sufficient conditions for the truth of a physical object proposition couched in terms that describe only connections between sensations. |
