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On Tuesday 21 August I will speak at a meeting of young scholars in the History and Philosophy of Logic and Mathematics in Leiden on “Logical Realism“.

The title of my talk is “Mathematics as a central issue in Brentanist descriptive psychology”. While there are lots of things I could discuss under this heading, I would like to take a step towards formulating a conclusion for my current research on the philosophy of mathematics in the School of Brentano and to situate it in the broader context of my VENI project on philosophy as science. Specifically, I will outline my findings regarding the existence and the basic elements of the Brentanist approach to the philosophy of mathematics and formulate an answer to the question of why mathematics constituted a central problem for the School of Brentano.

With the exception of Husserl’s case, the members of the School of Brentano have not generally been considered as being closely associated with mathematics. Therefore, it is quite remarkable to see that practically all of them sooner or later wrote and/or lectured on the philosophy of mathematics, and moreover did so more or less in the same timeframe. When considered as a whole, this strongly suggests the presence not just of a fortuitous common interest in the matter, but of a consciously shared theoretical core: a Brentanist philosophy of mathematics.

To show how the members of the School of Brentano reacted to and built on each other’s work, I will discuss the development of Husserl’s position in his early works out of the lectures of Brentano and Stumpf and their later reception among the Brentanists and others, including Husserl’s own retrospective evaluation of their significance. This illustrates both the coherence and unity of the School of Brentano as such as well as their synoptic approach to fundamental problems in philosophy and the sciences.