On Ehrenfels’ Dissertation

The present article provides a critical analysis of Christian von Ehrenfels’ dissertation Über Grössenrelationen und Zahlen. Eine psychologische Studie. As many other students of Brentano, Ehrenfels engaged repeatedly with the philosophy of mathematics, but until now his dissertation remained nearly completely unknown. Ehrenfels’ dissertation, however, fits perfectly within the Brentanist philosophy of mathematics and actually occupies an important place therein, precisely because it occurs outside of the vertical master - student lineage that goes from Brentano via Stumpf to Husserl. Indeed, Ehrenfels dissertation shows many parallels and anticipations to Husserl’s early works in the philosophy of mathematics