D - The Mechanical Aspect of the Circulation: Descartes and His Followers

Summary

CIRCULATION AND PHYSIOLOGY IN DESCARTES

Summary. (a) In contrast to Harvey's conception of science, Descartes does not determine the first principles of his natural philosophy in inductive fashion, but through an immediate conceptual assertion: his basic concepts are geometric matter devoid of qualities and the motion of its elementary particles. The concrete phenomena count as real only insofar as they can be derived from these abstract concepts. Deducibility is also the presupposition of practical production or at least of manipulation. Descartes sees in this the true goal of science. As the most general forms of natural as well as of artificial processes, the laws of nature become the most important principles in the study of nature. They constitute a world of purely mechanical causal connections to the exclusion of magical or teleological explanations.

(b) For physiology, this means the dualistic separation of bodily sensation and psychological experience from physical events in the body. The machine model of the organism, that is, the replacement of Harvey's autonomy of the organs by mechanistic automatism and the substitution of externally guided reflexes for selfmovement, is the basis for the first thoroughly “soulless” physiology, which is thus “scientific” in the modern sense.

(c) In what follows, we examine how, primarily through conceptual reinterpretation, Descartes isolates the material level of Galenic physiology and thus, without gaining essentially new knowledge, nevertheless interprets bodily processes in a wholly new way. Thus in Descartes the calor innatus, the “vital heat,” becomes an exothermic reaction of particles, that is, an event indistinguishable from purely inorganic, physico-chemical processes. This reaction provides the driving force for the cardiac motor and thus for the whole bodily machine. On the other hand, the reinterpretation of the spirits as a neuronal stream of particles makes possible a mechanical-cybernetic model of the control and movement of the organism. But it is the circulation that produces the decisive connection between triggering and control, now conceived as a “transmission belt”, but also as a circular feedback system. Instead of the vital independence of the organs, as in Harvey's conception, we have in the end their total subordination to the central nervous system; and in the Cartesian theory of the passions, the heart too—in the first instance only, in its role in the origin of the emotions—is tied to central control.