Saul Kripke

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Western Philosophy 20th Century
Name:	Saul Kripke
Birth:	1940
School/tradition:	Analytic philosophy
Main interests:	Logic (particularly modal logic), Philosophy of language
Notable ideas:	Causal theory of reference, Kripkenstein
Influences:	Frege, Bertrand Russell, Tarski, Ludwig Wittgenstein

Saul Aaron Kripke (born in November, 1940, Omaha, Nebraska) is an American philosopher and logician now emeritus from Princeton and professor of philosophy at CUNY Graduate Center. He has been immensely influential in a number of fields related to logic and philosophy of language. Much of his work remains unpublished or exists only as tape-recordings and privately circulated manuscripts. Kripke was the winner of the 2001 Schock Prize in Logic and Philosophy.

1 Biography
2 Work
3 Modal logic
4 Naming and necessity
5 Wittgenstein
6 Truth
7 Meaning of "I"
8 Notable publications by Kripke
9 Literature about Kripke
10 External links

[edit] Biography

Saul Kripke is the eldest of three children born to Dorothy and Rabbi Myer Kripke. His father was the leader of Beth El Synagogue, the only Conservative congregation in Omaha. His mother wrote Jewish educational children's books. Saul and his two sisters, Madeline and Netta, attended Dundee Grade School in Omaha and Omaha Central High School. He wrote his first essay at the age of sixteen on the semantics of modal logics. Reportedly, he was invited to come work at Princeton University based on this essay. He replied 'I'm honoured by your proposal, but my mum says I have to finish high-school first.' After graduating from high school in 1958, Kripke attended Harvard University, earning a bachelor's degree in mathematics. During his sophomore year at Harvard, Kripke taught a graduate level logic course at nearby MIT. For some years he taught at Harvard, moved to Rockefeller University in New York City in 1967, then to Cornell in 1977, and finally became a professor at Princeton University. In 2002 Kripke started teaching at the CUNY Graduate Center in midtown Manhattan, and was appointed a distinguished professor of philosophy there in 2003. Kripke married (and recently divorced) Margaret Gilbert. They have no children. He is a religious Jew.

[edit] Work

Kripke is best known for four contributions to philosophy:

Kripke semantics for modal and related logics, published in several essays beginning while he was still in his teens.
His 1970 Princeton lectures Naming and Necessity (published in 1972 and 1980), that significantly restructured the philosophy of language and, as some have put it, "made metaphysics respectable again"^{[citation needed]}.
His interpretation of the philosophy of Wittgenstein.
His theory of truth.

[edit] Modal logic

Two of Kripke's earlier works ("A Completeness Theorem in Modal Logic" and "Semantical Considerations on Modal Logic") were on the subject of modal logic. The most familiar logics in the modal family are constructed from a weak logic called K, named after Kripke for his contributions to modal logic.

In "Semantical Considerations on Modal Logic", published in 1963, Kripke responded to a difficulty with classical quantification theory. The motivation for the world-relative approach was to represent the possibility that objects in one world may fail to exist in another. If standard quantifier rules are used, however, every term must refer to something that exists in all the possible worlds. This seems incompatible with our ordinary practice of using terms to refer to things that only exist contingently.

Kripke's response to this difficulty was to eliminate terms. He gave an example of a system that uses the world-relative interpretation and preserves the classical rules. However, the costs are severe. First, his language is artificially impoverished, and second, the rules for the propositional modal logic must be weakened.

[edit] Naming and necessity

Kripke's three lectures constitute an attack on the descriptivist (Fregean, Russellian) theory of reference with respect to proper names, according to which a name refers to an object by virtue of the name's being associated with a description that the object in turn satisfies. He gave several examples purporting to render descriptivism implausible (e.g., surely Aristotle could have died at age two and so not satisfied any of the descriptions we associate with his name, and yet it would seem wrong to deny that he was Aristotle). As an alternative, Kripke adumbrated a causal theory of reference, according to which a name refers to an object by virtue of a causal connection with the object as mediated through communities of speakers. In this way, a name is a rigid designator: it refers to the named object in every possible world in which the object exists. Causal theories of reference have also been elaborated and developed by Michael Devitt, Keith Donnellan, David Kaplan, Hilary Putnam, Nathan Salmon, Scott Soames, Gareth Evans, and others, and are perhaps more widely held than descriptivist theories now. Notable holdouts include John Searle, Richard Rorty, and Alonzo Church; also notable is the fact that Hilary Putnam has drawn back from such a completely causal account.

Kripke also raised the prospect of a posteriori necessities—facts that are necessarily true, though they can be known only through empirical investigation. Examples include “Hesperus is Phosphoros”, “Cicero is Tully”, “Water is H₂0“ and other identity claims where two names refer to the same object.

Finally, Kripke gave an argument against identity materialism in the philosophy of mind, the view that every mental fact is identical with some physical fact (See talk). Kripke argued that the only way to defend this identity is as an a posteriori necessary identity, but that such an identity—e.g., pain is C-fibers firing—could not be necessary, given the possibility of pain that has nothing to do with C-fibers firing. Similar arguments have been proposed by David Chalmers.

Kripke delivered the John Locke lectures in philosophy at Oxford in 1973. Titled Reference and Existence, they are in many respects a continuation of Naming and Necessity, and deal with the subjects of fictional names and perceptual error. They have never been published and the transcript is officially available only in a reading copy in the university philosophy library, which cannot be copied or cited without Kripke's permission. In fact many copies are informally circulated among philosophers. Its influence, though considerable, is thus difficult to trace. However, it has been extensively referred to by some philosophers, particularly Gareth Evans and Nathan Salmon.

[edit] Wittgenstein

Kripke also made interesting contributions to the study of the later Wittgenstein in lectures published as Wittgenstein on Rules and Private Language, although his work here has been faulted for being not particularly true to the historical Wittgenstein. Indeed, many philosophers refer to the subject of Kripke's book as "Kripkenstein," on the grounds that the argument it presents would not have been endorsed by Wittgenstein. (For alternative readings of Wittgenstein, see Colin McGinn's Wittgenstein on Meaning.) The real significance of "Kripkenstein" was to give a clear statement for the idea that there is no fact in virtue of which a word has its meaning; this "meaning skepticism" generated a large secondary literature.

[edit] Truth

In his 1975 article "Outline of a Theory of Truth", Kripke showed that a language can consistently contain its own truth predicate, which was deemed impossible by Alfred Tarski, a pioneer in the area of formal theories of truth. The trick involves letting truth be a partially defined property over the set of grammatically well-formed sentences in the language. Kripke showed how to do this recursively by starting from the set of expressions in a language which do not contain the truth predicate, defining a truth predicate over just that segment: this adds new sentences to the language, and truth is in turn defined for all of them. Unlike Tarski's approach, however, Kripke's lets "truth" be the union of all of these definition-stages; after a denumerable infinity of steps the language reaches a "fixed point" such that using Kripke's method to expand the truth-predicate does not change the language any further. Such a fixed point can then be taken as the basic form of a natural language containing its own truth predicate. But this predicate is undefined for any sentences that do not, so to speak, "bottom out" in simpler sentences not containing a truth predicate. That is, "'Snow is white' is true" is well-defined, as is "'"Snow is white" is true' is true," and so forth, but neither "This sentence is true" nor "This sentence is not true" receive truth-conditions; they are, in Kripke's terms, "ungrounded."

[edit] Meaning of "I"

In late January 2006, Kripke attended a conference celebrating his 65th birthday and work at the Graduate Center of the City University of New York, and delivered a 70-minute talk on "The First Person", discussing the meaning and reference of the pronoun "I". (New York Times, January 28, 2006).

[edit] Notable publications by Kripke

1959. "A Completeness Theorem in Modal Logic", Journal of Symbolic Logic 24(1):1–14.
1962. "The Undecidability of Monadic Modal Quantification Theory", Zeitschrift für Mathematische Logik und Grundlagen der Mathematik 8:113–116
1963. "Semantical Considerations in Modal Logic", Acta Philosophica Fennica 16:83–94
1963. "Semantical Analysis of Modal Logic I: Normal Modal Propositional Calculi", Zeitschrift für Mathematische Logik und Grundlagen der Mathematik 9:67–96
1965. "Semantical Analysis of Intuitionistic Logic I", In Formal Systems and Recursive Functions, edited by M. Dummett and J. N. Crossley. Amsterdam: North-Holland Publishing Co.
1965. "Semantical Analysis of Modal Logic II: Non-Normal Modal Propositional Calculi", In The Theory of Models, edited by J. W. Addison, L. Henkin and A. Tarski. Amsterdam: North-Holland Publishing Co.
1971. "Identity and Necessity", In Identity and Individuation, edited by M. K. Munitz. New York: New York University Press.
1972 (1980). "Naming and Necessity", In Semantics of Natural Language, edited by D. Davidson and G. Harman. Dordrecht; Boston: Reidel. Sets out the causal theory of reference.
1975. "Outline of a Theory of Truth", Journal of Philosophy 72:690–716. Sets his theory of truth (against Alfred Tarski), where an object language can contain its own truth predicate.
1977. "Speaker's Reference and Semantic Reference", Midwest Studies in Philosophy 2:255–276
1979. "A Puzzle about Belief", In Meaning and Use, edited by A. Margalit. Dordrecht and Boston: Reidel.
1980. Naming and Necessity. Cambridge, Mass.: Harvard University Press. ISBN 0-674-59845-8 and reprints 1972.
1982. Wittgenstein on Rules and Private Language: an Elementary Exposition. Cambridge, Mass.: Harvard University Press. ISBN 0-674-95401-7. Sets out his interpretation of Wittgenstein aka Kripkenstein.
2005. "Russell's Notion of Scope", Mind 114:1005–1037

[edit] Literature about Kripke

G.W. Fitch (2005), Saul Kripke. ISBN 0-7735-2885-7.
Scott Soames (2002), Beyond Rigidity: The Unfinished Semantic Agenda of Naming and Necessity. ISBN 0-19-514529-1.
Christopher Hughes (2004), Kripke : Names, Necessity, and Identity. ISBN 0-19-824107-0.