To many contemporary scholars, Émile Meyerson is a footnote in an obscure history: early twentieth-century French philosophy of science. While the traditions of épistémologie are beginning to enjoy the scrutiny they deserve, Meyerson’s role remains overlooked. This article provides an overview of Meyerson’s philosophical project to help sow the seeds for a more systematic recuperation of its legacy. By orienting his work historically, I elucidate the nature of Meyerson’s critique of positivism, his distinctive method, and the implications these have for (...) the relation between science and philosophy. In particular, I show that for Meyerson positivisme refers not only to the doctrine of Auguste Comte but to a general philosophical tendency. Inseparable from Meyerson’s critique of this tendency is his implementation of a new methodology—épistémologie—according to which reason must be understood through the historical development of science. Épistémologie reveals that positivism not only is an incomplete account of science but is detrimental to its progress. Accordingly, Meyerson hopes to secure science’s right to function according to its own immanent principles, thereby providing prolegomena to all future metaphysics through a historical determination of the nature and limits of human reason. (shrink)