Logical positivism began to form a fairly definite outlook in philosophy about forty years ago. As is well known, it was primarily the influence of Ludwig Wittgenstein and Rudolf Carnap that initiated the early phase of this — then new and radical — departure from the traditional ways of philosophizing. To be sure, some aspects of logical positivism are derived historically from Hume and Comte; but, in contrast, especially to Mill's positivism, a new conception of logic (having its origins in Leibniz, Frege, and Russell) was united with the empiricism of Hume, Mach, and the early Einstein.