Highlighting early modern medicine's program of explanation and intervention, I claim that there are two distinctive features of the physician's naturalism. These are, first, an explicit recognition that each patient had her own individual and highly particularized nature and, second, a self-conscious use of normative descriptions when characterizing a patient's nature as healthy (ordered) or unhealthy (disordered). I go on to maintain that in spite of the well documented Cartesian rejection of Aristotelian natures in favor of laws of nature, Descartes (...) and his most important medical disciple accepted both features of the physician's naturalism where human medicine was concerned. Thus, in this article I critically engage with standard portraits of Cartesianism and naturalism by integrating the histories of science, medicine and philosophy, but especially medicine and philosophy. (shrink)