different disciplines. For example, Frege and later Russell were mathematicians, Boltzmann and Mach were physicists. Earlier Bolzano and then Brentano were originally theologians, and Meinong was a historian. 1 The sciences with their new insights and theories offered an enormous wealth of information which needed to be absorbed philosophically; but traditional philosophy could not deal with it. Physics presented a picture of reality which did not fit into the traditional schemes of empiricism or idealism. Ontological and epistemological questions became once again wide open issues. For example, atoms at first were still considered to be theoretical entities.