Saul Kripke

Saul Kripke (Bay Shore, New York, 1940 – 2022) was an American philosopher and logician whose work spanned modal logic, the philosophy of language, metaphysics and the theory of truth. From the 1960s until his death he was a central figure in analytic philosophy, and he is widely regarded as one of the most influential thinkers of his era. His name is tied to a way of understanding reference and necessity that changed how philosophers discuss proper names.

He was the eldest of three children of a Conservative rabbi and a mother who wrote books for the Jewish education of children. The family moved to Omaha, Nebraska, where he spent most of his childhood and was educated in local schools. He is said to have written a paper on the semantics of modal logic while still a teenager, and although the popular story of a Princeton job offer linked to it is often repeated, Kripke himself repeatedly said it was not true. He graduated in mathematics from Harvard with the highest honours and soon taught advanced logic, first at Harvard, then at Rockefeller University, Cornell and finally Princeton, where he became professor emeritus. In his last years he taught at the CUNY Graduate Center.

His first major contribution lay in modal logic. In his early work of the early 1960s he proposed a semantics based on possible worlds and accessibility relations between them, now known as Kripke semantics. It gave rigorous model theory to logics that had previously lacked one, and the basic normal modal logic K is named after him.

His most widely read work is Naming and Necessity, based on lectures given at Princeton in 1970 and published as a book in 1980. There he attacked the idea that a proper name refers to an object because the object satisfies a description attached to it. Kripke argued that names are rigid designators, picking out the same individual in every possible world where that individual exists, and that reference depends on a causal chain of use within a community of speakers. This distinction between necessity and the a priori allowed him to argue that some necessary truths are known only empirically, such as that water is H2O. The approach revived metaphysics and the discussion of essence after the decline of logical positivism.

Kripke also worked on the philosophy of mind, where he argued against simple identifications of mental and physical states, and on Wittgenstein. In Wittgenstein on Rules and Private Language he offered a reading of the problem of following a rule, which gave rise to the ironic name Kripkenstein; scholars still debate how faithful it is to Wittgenstein. In 1975 he published an article showing how a language can consistently contain its own truth predicate, something Tarski had considered impossible.

Much of his work was never published in his lifetime. It circulated as tape recordings and manuscripts, such as the Locke lectures Reference and Existence, which many philosophers knew informally. His influence is most visible in how reference, modality and truth are discussed today, and in the renewed respectability of metaphysics within analytic philosophy.