Carl Stumpf’s Philosophy of Mathematics

Like most of Franz Brentano’s students, Carl Stumpf showed an interest in the philosophy of mathematics. In particular, Stumpf wrote his habilitation thesis On the Foundations of Mathematics, used mathematical examples in central parts of his lectures, and later returned to the topic in the posthumously published Erkenntnislehre. I will try to show the development and the continuity of Stumpf’s position on the basis of his writings and (unpublished) lectures on logic and psycholo- gy, taking into account the Brentanist approach to the philosophy of mathematics that developed in the 1880s and 1890s in the School of Brentano.