This article has two parts. In the first part, I trace the development of Gottlob Frege's views
on the foundations of arithmetic, from the conception of logicism to the attempt to lay geometrical
foundations for arithmetic. I trace Frege's path from 1902, when he learned of Russell's paradox in the
system of The Basic Laws of Arithmetic, to the late manuscripts "Sources of Knowledge of
Mathematics and Mathematical Sciences", "Numbers and Arithmetic" and "A New Attempt at the
Foundations of Arithmetic", written in 1924/25, but not published until 1969. Between 1910 and
1924/25, Frege abandoned important theses of logicism.
¶ In the second part of the article, I discuss the philosophical sources of mathematics. There were
fundamental philosophical influences on Frege's new position. The views on the philosophy of
mathematics, especially on the concept of geometric intuition, of the neo-Kantian philosophers Bruno
Bauch and Richard Hönigswald provided the intellectual background to Frege's ideas. Bauch, who
was a good friend of Hönigswald, was Frege's colleague at Jena University between 1911 and 1918.
He had very good relations with Frege during this period.
¶ I want to examine Bauch's and Hönigswald's influences on Frege. Therefore I analyse the papers
of these philosophers and present the philosophical arguments in Frege's late essays. These arguments
were included in the neo-Kantian context of discussions about the philosophy of mathematics. This
fact is an important cause for Frege's having disregarded the contemporary discussion of the
paradoxes of set theory.