Saul Kripke, “Identity and Necessity” Driving question: How are contingent identity statements possible? For example, we take it to be the case that it is contingent that the first postmaster of the United States is identical with the inventor of bifocals (i.e. Benjamin Franklin). (73b)

An apparent paradox 1)(  x)(  y)[(x = y)  (Fx  Fy)] Law of substitutivity 2)(  x)  (x = x) Every object is necessarily self-identical 3)(  x)(  y)(x = y)  [  (x = x)   (x = y)] Substitution for (1) 4)(  x)(  y)((x = y)   (x = y))

The paradox with proper names “It would, therefore, seem that the function of names is simply to refer, and not to describe the objects so named by such properties as ‘being the inventor of bifocals’ or ‘being the first Postmaster General’.” (74b) And so, it would seem that “a” and “b” stand for names, it would seem that we should be able to make the following claim: (a = b  Fa)  Fb.

Identities in science Water is H 2 O. Heat is molecular motion. Gold has atomic number 79 [i.e. is a 79 proton kinda thing]. Kripke’s view: identities are necessary if true. (76b)

Rigid vs. nonrigid designators Please note: “rigid” not “ridged”! Rigid designator – a term that designates the same object in all possible worlds. (77a) What does this mean? What does it mean to talk about different possible worlds?

A multiplicity of possible worlds W  W´ “43 rd Pres.”“Loser in 2000”“Bush”“Gore” “2000 Loser”“43 rd Pres.”

“Bush” and “Gore” are rigid designators. “43 rd President” and “Loser in 2000” are nonrigid designators. Why? Because they can refer to (designate) different things in different possible worlds. Kripke’s claim is that natural kind terms are also rigid designators. What’s a natural kind? Water, Tiger, Trout, Gold, and so on. Terms that we use “to cut nature at its joints”.

Analytic, necessary, a priori, certain. “What do we mean by calling a statement necessary? We simply mean that the statement in question, first, is true, and, second, that it could not have been otherwise. When we say that something is contingently true, we mean that, though it is in fact the case, it could have been otherwise. If we wish to assign this distinction to a branch of philosophy, we should assign it to metaphysics. To the contrary, there is the notion of an a priori truth. An a priori truth is supposed to be one which can be known to be true independently of all experience…. Now, this notion, if we were to assign it to a branch of philosophy, belongs, not to metaphysics, but to epistemology.” (79b) Kripke continues: “Now I hold, as a matter of fact, that neither class of statements is contained in the other. But all we need to talk about here is this: Is everything that is necessary knowable a priori or know a priori?” (80a)

The problem of essentialism. What are the properties that are essential to x? Kripke’s example of the lectern. Could it have been made of ice? (80b) If essentialism is correct, then we will have necessary a posteriori truths. p   p p______   p E.g. if the lectern were not made of ice, then it was necessarily not made of ice.

Kripke shows that identity is, in cases of names and theoretical identifications, necessary. E.g.Cicero is Tully Mark Twain is Samuel Clemens Heat is molecular motion Water is H2O But not Bush is the 43rd President Why? Because there is a possible world in which Gore was elected the 43rd President.

A sketch of Kripke’s argument 1)Water is H2O in the actual world. 2)If water is H2O in the actual world, then water is H2O in every possible world. 3)Therefore, water is H2O in every possible world. 4)If something holds in every possible world, then it is necessarily true. 5)Therefore, it is necessarily true that water is H2O. The argument follows from truth of premises (1), (2), and (4). (3) follows from (1) and (2); (5) follows from (3) and (4).