The aim of this book is to defend rationality against skepticism fideism, and irrationalism. Rationality is an ideal which represents the best in our civilization. The ideal, however, must be reaffirmed from time to time and this is done here by expressing it in a contemporary idiom and by defending it against new doubts. Professor Kekes justifies rationality most convincingly at the same time he demonstrates how important philosophy is for the preservation of the finest in Western tradition.