First published in 1995. When did psychology become a distinct discipline? What links the continental and analytic traditions in philosophy? Answers to both questions are found in this extraordinary account of the debate surrounding psychologism in Germany at the turn of the century. The trajectory of twentieth century philosophy has been largely determined by this anti-naturalist view which holds that empirical research is in principle different from philosophical inquiry, and can never make significant contributions to the latter's central issues. Martin Kusch explores the origins of psychologism through the work of two major figures in the history of twentieth century philosophy, Gottlob Frege and Edmund Husserl. His sociological and historical reconstruction shows how the power struggle between the experimental psychologists and pure philosophers influenced the thought of these two philosophers, shaping their agendas and determining the success of their arguments for a sharp