This is a concise and readable study of five intertwined themes at the heart of Wittgenstein's thought, written by one of his most eminent interpreters. David Pears offers penetrating investigations and lucid explications of some of the most influential, and yet puzzling writings of twentieth-century philosophy. He focuses on the idea of language as a picture of the world; the phenomenon of linguistic regularity; the famous 'private language argument'; logical necessity; and ego and the self.