Abstract
This essay discusses the unity of mathematics by comparing the philosophies of Mill and Frege. While Mill is remembered as a progressive social thinker, his contributions to the development of logic are less widely heralded. In contrast, Frege made important and lasting contributions to the development of logic while his social thought, what little is known of it, was very conservative. Two theses are presented in the paper. The first is that in order to pursue Mill’s progressive sociopolitical project, one must embrace Frege’s distinction between logic and psychology. The second thesis is that in order to pursue Frege’s project of accounting for the unity of mathematics, we must understand mathematics as a human activity and consider the role that history and psychology play in the growth of mathematics.