Saul Aaron Kripke
(born on November 13
in Bay Shore, New York
) is an American philosopher
, now emeritus
. He teaches as distinguished professor of philosophy at CUNY Graduate Center
. Kripke has been 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 Much of his work remains unpublished or exists only as tape-recordings and privately circulated manuscripts.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 recipient of the 2001 Schock Prize
in Logic and Philosophy.
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
. After graduating from high school in 1958, Kripke attended Harvard University
, earning a bachelor's degree
. 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 Princeton University
full-time in 1977. 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 subsequently divorced) the philosopher Margaret Gilbert
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"
- His interpretation of the philosophy of Wittgenstein.
- His theory of truth.
Two of Kripke's earlier works ("A Completeness Theorem in Modal Logic" - written while he was still a teenager - 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 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.
Kripke's possible worlds theory has been used by narratologists (beginning with Pavel and Dolezel) to understand "reader's manipulation of alternative plot developments, or the characters' planned or fantasized alternative action series" (Fludernik). It has become especially useful in the analysis of hyperfiction.
Naming and necessity
Kripke's three lectures constitute an attack on descriptivist theories of proper names
. Kripke attributes variants of descriptivist theories to Frege
, Ludwig Wittgenstein
and John Searle
, among others. According to descriptivist theories, proper names either are synonymous with descriptions, or have their reference determined by virtue of the name's being associated with a description or cluster of descriptions that an object uniquely satisfies. Kripke rejects both these kinds of descriptivism. He gives several examples purporting to render descriptivism
implausible as a theory of how names get their reference determined (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. Kripke holds that the meaning of a name simply is the object it refers to. To show this, he points out that proper names, in contrast to most descriptions, are rigid designators
: A proper name refers to the named object in every possible world
in which the object exists, while most descriptions designate different objects in different possible worlds. For example, 'Nixon' refers to the same person in every possible world in which Nixon exists, while 'the person who won the United States presidential election of 1968
' could refer to Nixon
, Humphrey, or others in different possible worlds.
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 Phosphorus”, “Cicero is Tully”, “Water is H2O” 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.
Claims of Historical Influence
In a 1995 paper, philosopher Quentin Smith
argued that key concepts in Kripke's new theory of reference
had originated from the work of Ruth Barcan Marcus
more than a decade earlier. Smith identified six significant ideas to the New Theory which he claimed that Marcus had developed:
- The idea that proper names are direct references, which don't consist of contained definitions.
- While one can single out a single thing by a description, this description is not equivalent with a proper name of this thing.
- The modal argument that proper names are directly referential, and not disguised descriptions.
- A formal modal logic proof of the necessity of identity.
- The concept of a rigid designator, although the actual name of the concept was coined by Kripke.
- The idea of a posteriori identity.
Smith proceeded to argue that Kripke failed to understand Marcus' theory at the time, yet later adopted many of its key conceptual themes in his New Theory of Reference.
Several scholars have subsequently offered detailed responses showing that no plagiarism occurred..
A Puzzle about Belief
Kripke’s main propositions in Naming and Necessity concerning proper names are, that the meaning of a name simply is the object it refers to, and that a name’s referent is determined by a causal link between some sort of “baptism” and the utterance of the name. Nevertheless he acknowledges the possibility that propositions containing names may have some additional semantic properties, properties that could explain why two names referring to the same person may give different truth values in propositions about beliefs. (Lois Lane believes that Superman can fly, although she does not believe that Clark Kent can fly. This can be accounted for if the names “Superman” and “Clark Kent”, though referring to the same person, have distinct semantic properties.)
In the article “A Puzzle about Belief” Kripke seems to oppose even this possibility. His argument can be reconstructed in the following way: The idea that two names referring to the same object may have different semantic properties, is supposed to explain that coreferring names behave differently in propositions about beliefs. (Like in Lois Lane's case.) But the same phenomenon occurs even with coreferring names that obviously have the same semantic properties:
Kripke invites us to imagine a French, monolingual boy, Pierre, who believes the following: “Londres est jolie.” (“London is beautiful.”) Pierre moves to London without realising that London = Londres. He then learns English the same way a child would learn the language, that is, not by translating words from French to English. Pierre learns the name “London” from the unattractive part of the city he lives in, so he comes to believe that London is not beautiful. If Kripke’s account is correct Pierre now believes both that London is beautiful and that London is not beautiful. This cannot be explained by coreferring names having different semantic properties. According to Kripke, this shows that attributing additional semantic properties to names, will not explain what it is supposed to explain.
Kripke also contributed 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 misrepresenting 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 put forward a clear statement of a new kind of scepticism, dubbed "meaning scepticism", which is the idea that for an isolated individual there is no fact in virtue of which he/she means one thing rather than another by the use of a word. Kripke's "sceptical solution" to meaning scepticism is to ground meaning in the behaviour of a community. Kripke's book generated a large secondary literature, divided between those who find his sceptical problem interesting and perceptive, and others (such as Gordon Baker
and Peter Hacker
) who argue that his meaning scepticism is a pseudo-problem that stems from a confused, selective reading of Wittgenstein. Kripke's position has recently been defended against these and other attacks by the Cambridge philosopher Martin Kusch
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."
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".
Kripke is a devoutly religious Jew. Additionally, in an interview with Andreas Saugstad, he stated "I don't have the prejudices many have today, I don't believe in a naturalist world view. I don't base my thinking on prejudices or a world view and do not believe in materialism."
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 on 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.
- 1976. "Is There a Problem about Substitutional Quantification?", In Truth and Meaning: Essays in Semantics, edited by Gareth Evans and John McDowell. Oxford: Oxford University Press.
- 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
Literature about Kripke
- Arif Ahmed (2007), Saul Kripke. New York, NY; London: Continuum. ISBN 0826492622.
- G.W. Fitch (2005), Saul Kripke. ISBN 0-7735-2885-7.
- Christopher Hughes (2004), Kripke : Names, Necessity, and Identity. ISBN 0-19-824107-0.
- Consuelo Preti (2002), On Kripke. Wadsworth. ISBN 0534583660
- Scott Soames (2002), Beyond Rigidity: The Unfinished Semantic Agenda of Naming and Necessity. ISBN 0-19-514529-1.