In trying to estimate the work of a particular philosopher it seems natural enough to begin with a description of the history and circumstances of the man himself. And yet it is almost invariably the case that most, if not all, of these biographical items are gradually lost sight of as the main business of interpreting and criticizing advances. We include our knowledge of the man in an introductory chapter, and rarely, if ever, refer to it. As a result, the philosopher and his work seem to be things apart. The work becomes a contribution to philosophy, distinguished, in a personal sense, from other contributions by little more than the convenient symbol of its author's name.