The time has long passed when it was necessary to explain or to justify philosophy of science to a convention of scientists. The growing intent among philosophers and scientists to clarify and perhaps to unify the programs, methods, and results of the disciplines of philosophy and science is matched by a growing determination among the special sciences to cooperate in the examination of fundamental concepts and presuppositions in the light of the positive results of science, to cooperate in the systematic doubting of these positive results, and to cooperate in the thoroughgoing analysis and critique of logic and of language,—all of which are projects which can be carried out only by the joint effort of philosophers and scientists. In short, it has long since been realized that the special sciences cannot safely be abandoned to their devotees, exclusively. It was only twenty-five years ago that Santayana was able to say “I would gladly learn more of contemporary thinkers if they would only learn more of each other.” The implication that lies in that statement is hardly the case today, when the synoptic enterprise of philosophy-of-science is helping the scientific thinker to recognize the limitations of his task and the assumptions with which he starts, and to save him from being too easygoing in the criticism of his categories.