Saul Kripke Identity And Necessity

Saul Kripke's highly influential “Identity and Necessity” challenges a number of prevalent assumptions made by his contemporaries regarding the classification of identity statements as either contingent or necessary. (Heide, 26 Feb.) Firstly, he renounces the common habit of speaking of necessary truths, those that could not have possibly have been false, as being equivalent to a priori truths, or those knowable without the aid of sensory experience. (Kripke 130) Secondly, he argues for a theory of identity that drastically diverges from others of the time. Kripke offers an explanation of how some identity statements, in particular those involving only descriptive terms, can be contingently true. He differentiates these from other identity …show more content…
Some hold that sentences like “Hesperus is Phosphorus,” with both terms referring to the planet Venus, are truths discoverable a posteriori via scientific inquiry and must be contingent, as they could have turned out to be false. (125) Kripke rejects this view, employing the terms “rigid designator” and “nonrigid designator” to illustrate their necessity. Nonrigid designators are descriptions, like those utilized in the Benjamin Franklin statement, and pick out an individual only contingently. Proper names are rigid designators which, on the other hand, locate the same individual in every possible world or counterfactual scenario. Whereas nonrigid designators, such as “the first Postmaster General of the United States,” are contingent because it could have been another individual that satisfies them, rigid designators, such as “Hesperus” and “Phosphorus,” must be necessary, or true in all possible worlds. (127-128) In every possible world that the planet Venus exists, the names “Hesperus” and “Phosphorus” will pinpoint it. (128) Kripke provides a brief thought experiment to prove this: The statement “the square root of 81” is a rigid designator in that it will always refer to 9, for it is impossible to conceive of this statement singling out some other number. Similarly, the proper name “Hesperus,” a name we ascribed to …show more content…
Though tied to one another in the actual world, this does not necessarily have to be the case in other worlds. In fact, it seems as though we can conceive, with relative ease, of a possible world in which “heat” designates the sensation of heat and “molecular motion” designates the activity of molecules, yet they designate different phenomena existing simultaneously. Unlike the proper names statement, there seems to be no unacceptable conclusion generated when the two names are separated from one another in the same possible world. Here, perhaps heat is caused by a deity willing the sensation to occur, and molecular motion instead results in the appearance of the smell of roses. “Heat” still refers to the sensation of heat as we experience it on earth, it just happens to lack a relation to molecular motion. Similarly, “molecular motion” still refers to the movement of molecules, it just involves an entirely different sensation than that of heat. In this world, how could it be said that “heat is the motion of molecules” if the two designators identify different phenomena that are occurring at the same time, isolated from one another? Both terms are rigid designators, yet do not seem to be conceptually constrained to one another as “Hesperus” and “Phosphorus” are. Therefore, it seems problematic to compare theoretical identifications to statements containing proper names and to assert that they,