Saul Kripke Gave Three Lectures Without Notes at 29, and It Reset Modern Philosophy

In January 1970, the 29-year-old Saul Kripke delivered three lectures at Princeton on the philosophy of language. He spoke without notes, having no fully written draft. The lectures were recorded, transcribed, and published verbatim in 1972 in Semantics of Natural Language; Harvard University Press reissued them as a stand-alone book, Naming and Necessity, in 1980. The book runs about 170 pages, it does not have a numbered argument structure, and Scott Soames now ranks it among the most important works of analytic philosophy ever published.

The central move is small and devastating. Kripke distinguishes between two questions a philosopher had until then often run together. The first is: must this thing be the case? — a question of necessity. The second is: how do we come to know this thing is the case? — a question of knowledge. Kant had assumed the necessary truths were precisely those knowable a priori, by armchair reasoning. Kripke pulled the two apart. Some statements, he argued, are necessary truths but knowable only by empirical investigation. "Water is H₂O," if true, is necessary; in any possible world where the substance with the right molecular structure exists, that's water. But you cannot derive H₂O from the meaning of water. You have to go and look.

The machinery he used to do this — "rigid designators," names that pick out the same individual in every possible world — sank, over the next two decades, into how philosophers thought about identity, reference, and modality. The book also gave "a posteriori necessity" a working semantics, supplied a causal theory of how proper names refer, and quietly demolished the descriptivist orthodoxy that had run from Frege through Russell. None of it was written down before the lectures.