Well into the 1940s, many French biologists rejected both Mendelian genetics and Darwinism in favour of neo-transformism, the claim that evolution proceeds by the inheritance of acquired characteristics. In 1931 the zoologist Maurice Caullery published Le Problème d’évolution, arguing that, while Lamarckian mechanisms could not be demonstrated in the present, they had nevertheless operated in the past. It was in this context that Raymond Aron expressed anxiety about the relationship between biology, history, and human autonomy in his 1938 Introduction à (...) la philosophie de l’histoire: essai sur les limites de l’objectivité historique, in which he rejected both neo-Kantian and biological accounts of human history. Aron aspired to a philosophy of history that could explain the dual nature of human existence as fundamentally rooted in the biological, and at the same time, as a radical transcendence of natural law. I argue that Aron’s encounter with evolutionary theory at this moment of epistemic crisis in evolutionary theory was crucial to the formation of his philosophy of history, and moreover that this case study demonstrates the importance of moving beyond the methodological divisions between intellectual history and history of science. (shrink)