Modern empiricism is usually thought to have emerged in opposition to the then dominant school of neo-Kantianism. True as this may be, it has blinded us to the fact that Kantian and more surprisingly even neo-Kantian elements of philosophy have also had a positive influence upon the development of the new empiricism. One episode in which this influence proves itself in fact dominant and which I will present in the following concerns the philosophical position which Popper adopted vis-à-vis logical empiricism — as advocated by Wittgenstein and Schlick — in Vienna in the late twenties and early thirties of the last century.