 In his position as a natural philosopher, in dialogue with the works of Newton, Descartes, Leibniz, Clairaut, the French Encyclopedists, and major English philosophers of his period, Buffon explored foundational methodological and philosophical questions of the Enlightenment in combination with his analysis of empirical questions. One expression of this wider vision was the unusual way in which he sought to validate the inquiry into natural history in relation to a naturalized epistemology that scholars have seen as novel for its time (Hoquet 2005; Sloan 2006b; Roger 1963 [1997: chp. 9], 1989 [1997: chp. 6]). In developing a new methodological approach to natural history, Buffon claimed to ground his arguments on a form of empirical certitude—“physical truth” [verité physique]—attained through inquiries into the concrete relations of beings in their material relations. This he opposed to the “abstractions” of mathematical physics, extending, it seems, the Leibnizian-inspired argument against Newton as developed in Émilie Du Châtelet’s (1706–1749) Institutions de Physique, a work Buffon is known to have read and admired as he made his transition into his career in natural history (Sloan 2019). Developing this argument in a long “Discourse on Method” that opened the first volume of his Histoire Naturelle (Natural History) (1749), Buffon argued that a science based on repeated observation of concrete material relations of bodies can achieve a degree of epistemic certitude that surpasses that available from the mathematical analysis of nature (Hoquet 2005; Grene &amp; Depew 2004; Roger 1989 [1997: chp. 6]; Sloan 2006b). On the basis of this novel epistemological framework, oriented to the search for “physical” truth, Buffon thus directed natural history away from a primarily classificatory project. The latter project, exemplified by the work of his contemporary Linnaeus, Buffon criticized for imposing “abstract” categories on nature. In its place, Buffon sought to analyze living beings in relation to their material conditions of existence. This was to be focused on their reproductive relationships, biogeographical distribution, and in his later work, on their connections to cosmology and historical geology.