Abstract
Historians have convincingly shown the extent to which Protestantism played a role in the founding of the Third Republic, undermining the once canonical claim that republicanism and religion were implacably hostile opponents in the latter half of the nineteenth century. Catholics, however, continue to be viewed as nearly universally antirepublican. Analyzing the writings of philosopher Emile Boutroux and his students, this article shows how the specifically Catholic concern with the relationship between free will and scientific concepts of determinism both influenced the direction of French philosophy of science into the twentieth century and provided a framework for defending the Republic at the height of the Dreyfus affair