term1 Definition1term2 Definition2term3 Definition3
Please sign in to your Google account to access your documents:
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.
Mind—body dualismCartesian 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.
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.
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.
MonismThe 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.
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.
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.
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.)
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.
Central state materialism
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 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.
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.
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?
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.
Cognitive psychology, content, and consciousnessCognitive 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.
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.
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.
Mind—body dualism
Cartesian dualism
Monism
The dual-aspect theory
Cognitive psychology, content, and consciousness
Cognitive psychology
Need help typing ? See our FAQ (opens in new window)
Please sign in to create this set. We'll bring you back here when you are done.
Discard Changes Sign in
Please sign in to add to folders.
Sign in
Don't have an account? Sign Up »
You have created 2 folders. Please upgrade to Cram Premium to create hundreds of folders!