Attentiveness to the anatomy and physiology of the human body, and to its proper management in health and disease, is evident in many of Descartes’ formal publications, and he several times states that the goal of his natural philosophy is to prolong life. Many of his closest associates in the Netherlands – where he wrote his major works – are physicians or have a medical education, including Isaac Beeckman, Cornelis Van Hogelande, Vopiscus Fortunatus Plempius, Henricus Regius, and Henri Reneri. Descartes is even offered a professorship of theoretical medicine at Bologna in 1633 (Manning 2013). In the mid-1640s, he acts as a medical adviser as well as philosophical interlocutor to Princess Elisabeth. At the same time, a version of his views presented in the medical faculty at the University of Utrecht by Regius led to the first major dispute about Cartesianism. His last works – the Passions of the Soul (1649) and the posthumous Description of the Human Body – confirm that up to the last he continued to devote much effort to questions of physiology and mind-body interactions.

Descartes begins to study animal bodies almost from the beginning of his move to the Netherlands; they remain of interest to him throughout his life and undergird one of the chief aims of his studies, the prolongation of human life. Soon after embarking on an ambitious project “to explain all the phenomena of nature” he writes, “I am now studying chemistry and anatomy simultaneously; every day I learn something that I cannot find in any book” (AT I 137, CSMK 21). Descartes investigates the world through expériences (often translated as “observations” or “experiments”), and he expects his readers to do the same. In the section on human physiology in the Treatise on Man, Descartes explains: “I assume that if you do not already have sufficient first-hand knowledge of [the parts of the human body], you can get a learned anatomist to show them to you – at any rate, those which are large enough to be seen with the naked eye” (AT XI 120–21, CSM I 99).