Originally published in 1966. This volume analyzes the general structure of scientific theories, their relation to experience and to non-scientific thought. Part One is concerned with the logic underlying empirical discourse before its subjection to the various constraints, imposed by the logico-mathematical framework of scientific theories upon their content. Part Two is devoted to an examination of this framework and, in particular, to showing that the deductive organization of a field of experience is by that very act a modification of empirical discourse and an idealization of its subject matter. Part Three analyzes the concordance between theories and experience and the relevance of science to moral and religious beliefs.