 One of Stumpf’s arguments in favour of interactionism and against parallelism is Darwin’s theory of evolution (Stumpf, 1910, p. 78–79) to which he attaches great importance since the 1880s (E. Valentine, 2000) In an article entitled “Der Entwicklungsgedanke in der gegenwärtigen Philosophie,” Stumpf compares the bearing of Darwin’s theory on science to that of the Copernican revolution in astronomy. (Stumpf, 1899a) Stumpf’s interest in Darwin’s theory is clearly expressed in his work on psychophysical relations, the origins of music, animal psychology as well as in those on child development.