"Psychologism" was a name used by some philosophers in their criticism of a specific research program. The aim of the program was to solve all questions of epistemology, those referring to logic and mathematics included, with the aid of psychological research. This research program was wide spread in the second half of the nineteenth century among such philosophers and psychologists as John Stewart Mill, Herbert Spencer, Wilhelm Dilthey, Franz Brentano, Carl Stumpf, the early Husserl and others. The list of names indicates that quite different paradigms of psychology have been used in this research program.