In 1970, Saul Kripke gave a series of three lectures at Princeton University. These lectures, subsequently published under the title _Naming and Necessity_, were quickly recognized as one of those rare events that turns the world of philosophy on its ear. Amazingly, Kripke was a mere 29 years old at the time and he delivered the lectures without any notes. This book reflects both the advantages and shortcomings of the spoken form: it is clear, engaging, and often witty, but it is also repetitive at times and frustratingly incomplete at others.
It is perhaps fitting that Kripke delivered these lectures the same year that Bertrand Russell passed away, since their main target is the descriptivist theory of names associated with Russell. According to Russell - and to the reigning philosophical orthodoxy until 1970 - names are best analyzed as abbreviated definite descriptions, i.e. as unique sets of properties possessed by their bearers. However, Kripke argues that on this analysis, all such properties belong to their possessors necessarily - which is obviously false. For instance, if the name "Billy Strayhorn" just means "The composer of 'Take the "A" Train,'" then there is no possible world in which Billy Strayhorn did not compose the song. But this is false: Even if Billy Strayhorn had never written any songs, he would obviously still be Billy Strayhorn. What a puzzle!
In place of descriptivism, Kripke proposes the theory of direct reference, according to which a name "rigidly designates" its referent in every possible world in which it exists. That is, a name is just a "tag" attached to its referent, with no descriptive content whatsoever. Kripke also proposes an alternative theory for how names are transmitted, the causal theory of names. For Kripke, the name I use for Strayhorn is "his" name in virtue of the fact that it is related, by means of some appropriate causal chain, to Strayhorn himself.
Much of this was anticipated by other philosophers, though this often goes unnoticed. But Kripke developed his theory in a highly interesting way and put it to all sorts of surprising uses. His discussion of necessity and possibility almost single-handedly resurrected essentialism and gave a major impetus to contemporary modal metaphysics. He claims that names for natural kinds, such as "gold" and "tiger," rigidly designate their referents and argues that this establishes the existence of necessary a posteriori truths. He closes the book by offering an essentialist argument against the mind-body identity thesis.
In short, Kripke has given philosophers much to talk about. Indeed, _Naming and Necessity_ has spawned a whole cottage industry of commentary. In my view, Kripke's project is flawed in many (though not all) respects. For instance, his causal theory is too vague to be of much use, and his argument that natural kind terms directly refer seems question-begging. Nonetheless, Kripke's book is extremely provocative, interesting, important, and even fun.