In “Metaphysics,” the first topic chosen is an old and traditional one—the nature of the self, the status of the individual. Nozick calls up an old and fascinating example: the ship of Theseus. If a plank wears out on the ship, it is thrown away and a new plank is fitted to the deck. Suppose all the planks and all the other equipment of the ship are similarly replaced: Does one still have the old ship, or is it a new one? As if that were not puzzling enough, suppose someone sneaks away with the discarded equipment and forms it into a ship again: Which ship is the old ship and which is the new one?
The problem is not concerned with ships but with people. The components of the body change constantly. Is one still the same person? This problem has to do with the body as material object; if this were the whole problem, it would be easy to solve, simply by denying that molecular interchange constitutes a material change. When mental “objects” are considered, however, the problem is not so easy to dismiss. For example, has a college class on philosophy changed if one of the students is absent? Or (Nozick’s example) if the famous Vienna Circle of philosophers had scattered before World War II (as it did), what would have happened to the Vienna Circle if three members had emigrated to Istanbul and carried on as the Vienna Circle, only to find out at the end of the war that other members had emigrated to the United States and also carried on as the Vienna Circle? Where would the “real” Vienna Circle have been located?
In his solution to this problem, Nozick seems to be analyzing not what the “individual” really is, but what is meant when the word “individual” is used, an approach credited to Ludwig Wittgenstein. Nozick employs the notion of the “closest continuer”; whichever of the entities to be traced bears the closest “continuing” relationship with the original object would be called “the original object.” Thus, in the case of Theseus’ ship, most people would say that the closest continuer would be the ship from which the planks were originally taken and replaced.
The second portion of “Metaphysics,” “Why Is There Something Rather than Nothing,” deals with a famous metaphysical question with which philosophers from Gottfried...
(The entire section is 941 words.)