Philipp Frank: A crusader for scientific philosophy -- Part I. Introduction: Science, facts, and values -- The longing for a humanization of science -- Metaphysical interpretations of science -- The sociology of metaphysical interpretations -- Philosophy of science and political ideology -- Sociology of science and the search for a democratic metaphysics -- Part II. Scholastic philosophy and Thomism -- The physical universe as a symbol -- Union, divorce, and reunion between science and philosophy -- Science, democracy, and the new wave of positivism -- The Vienna circle : Moritz Schlick, Rudolf Carnap, and Otto Neurath -- Pragmatism -- Mechanistic and dialectical materialism -- The laws and politics of dialectical materialism -- Conclusion: Einstein's philosophy of science.