Terence Parsons presents a lively and controversial study of philosophical questions about identity. Is a person identical with that person's body? If a ship has all its parts replaced, is the resulting ship identical with the original ship? If the discarded parts are reassembled, is the newly assembled ship identical with the original ship? Because these puzzles remain unsolved, some people believe that they are questions that have no answers, perhaps because the questions are improperly formulated; they believe that there is a problem with the language used to formulate them. Parsons explores a different possibility: that such puzzles lack answers because of the way the world is (or because of the way the world is not); there is genuine indeterminacy of identity in the world. He articulates such a view in detail and defends it from a host of criticisms that have been levelled against the very possibility of indeterminacy in identity.