La philosophie médicale de Descartes

Vincent Aucante. xxi + 472 pp. illus., figs., tables, app., bibl., index. Paris: Presses Universitaires de France, 2006. € 31.

(Originally published in Isis.)

It would be difficult to imagine a more thorough treatment of Descartes’s medical philosophy than the one Vincent Aucante has undertaken, and we may be certain this study will remain authoritative for some time to come.  It is to be hoped that an English translation will be published soon, as this book is of tremendous interest not only to specialists in the history of medicine, but to anyone interested in understanding Descartes in terms of what he himself sought to understand.  Medicine was important to Descartes: Aucante places at 20% the quantity of pages in the oeuvre dedicated to it, and Descartes himself writes in a 1645 letter that “the preservation of health has always been the principle aim of my studies” (AT IV 329).  In view of Descartes’s own stated priorities, the received view of the 19th-century neorationalists who saw Descartes’s medical thought as a failure, and as best left out of editions, urgently needs to be revised.  Aucante’s book makes this case powerfully. 

This study surpasses Annie Bitbol-Hespériès’s Le principe de vie chez Descartes of 1990 in depth and breadth, though the subject here is not, to be precise, life.  Life, for Descartes, is sustained by the ‘feu sans lumière’ (AT VI 46, 7-8) of the beating heart, and thus by a sort of ferment.  To this extent animals, lacking the souls Aristotle had thought all living things have in common, are perfectly alive.  Descartes’s ‘biology’ is thus entirely contained within his physics, while the ultimate horizon of his medicine is metaphysical, to the extent that medicine is concerned specifically with ensouled bodies, that is, human bodies, with their health and well-being, and with the psychophysical causes of disorders.  In Jean-Luc Marion’s terms in his short preface (these in turn borrowed from Husserl), medicine is concerned not so much with the body [le corps, der Körper] as with the flesh [la chair, das Leib, or, in Descartes’s own telling phrase, mon corps].

Because the nature of the body-soul union remains problematic for Descartes, and also because many of the precise mechanisms that would explain non-soul-based physiological processes such as conception remain unsatisfactorily worked out even by Descartes’s own admission, his medicine has the status of a science inachevée.  But Aucante sees its unfinished status as both a testament to Descartes’s philosophical integrity, as well as being for this same reason a better model for the emerging hypothetico-deductive sciences than the much more widely celebrated mathematics. Descartes’s medicine in Aucante’s account is both incomplete and exemplary. 

The subject of the first part of the book is ‘The Method,’ to which Descartes is devoted in all of his philosophical pursuits.  Ultimately, Descartes believes that his medicine could achieve that same force as mathematical demonstrations, even if it also depends on experience (148).  In view of its peculiar intermediary position between these two classical forms of knowledge, Aucante believes Descartes’s medicine must rely heavily on “modelles,” that is, ensembles of explanations that are “different from reality, but that nevertheless depict reality clearly, like an artist’s sketch” (424).  Descartes’s most important physiological model is that of ‘machine’, which helps him to understand the mechanical functioning of the organism, even if this model remains limited to the extent that it cannot possibly take into account the union of the soul and the body.  In this respect, the mechanical model is a starting point in Descartes’s physiology, but not the ultimate ending point of his medicine, which is itself as practical as theoretical, and which has health as its principal object. 

For Descartes, ‘physiology’ – which is the subject of the second and longest part of the book – constitutes the theoretical part of medicine, even if Descartes breaks with tradition in seeing the laws of physiology as being just those of physics.  Descartes hopes to explain all of physiology in terms of “the ordinary laws of nature,” but he also takes recourse to quite a few more natural phenomena than could apparently ever be reduced to basic laws, such as sympathy, impetus, the struggle [la lutte] of, e.g., the male and female semens with one another, and chance [le hasard].  Perhaps the example of sympathy is the most revealing of these.  Descartes retains it to explain, among other things, the bilateral symmetry of vertebrates and the influence of a pregnant woman’s imagination on the physiognomy of the developing fetus, while entirely abandoning the model of the body as microcosm that had underpinned Renaissance accounts of sympathy.  Here as elsewhere, Descartes retains concepts from pre-mechanist science, while drastically transforming their sense. 

Aucante emphasizes that by far the most important phenomenon in Descartes’s physiology is borrowed directly from physics, namely, fermentation.  By appeal to this Descartes is able to account not just for the heat of the heart, but also digestion and a number of other bodily processes.  Fermentation is the production of heat from corruption, and is thought responsible, at least from 1637 on, for conception and for certain aspects of fetal development.  The primary motor of generation is not some vegetative soul, but rather the dilatation of the male and female ‘semens’, of which the one acts as a sort of ‘leaven’ upon the other.  If there is no soul guiding development, it follows that an entity does not develop into some kind of creature or other as a result of the inherence of some species-specific form.  It follows from this, in turn, that, in so far as I am a thinking thing, I am not my parents’ child: my humanity does not emerge from sexual reproduction, even if the ordinary laws of nature are, Descartes hopes, enough to explain the formation of a complex organism from the mixture of seminal fluids.  Descartes never explicitly addresses the question as to when, exactly, the soul enters the fetus, though he does tell Regius that at a moment known only by God, the soul is created miraculously in each body (AT III 461, 3). 

The final two chapters, on illnesses and their treatment, constitute perhaps the most novel part of the book.  The only variety of illness Descartes ever thoroughly analyzed was fever, but he made enough passing references to scurvy, stones, phthisis, jaundice, etc., in his shorter anatomical excerpts for a general Cartesian pathology to be reconstructed by a careful scholar.  Descartes’s ‘therapeutics’, in turn, is mostly scattered throughout his correspondence, but Aucante’s presentation of these scattered comments reveals a thinker who sincerely believes that the health of the embodied person must be the foremost concern not just of the physician, but of the philosopher too.

Comments

[Willem van Hoorn]

This is indeed an excellent study. However, Aucante's claim that Descartes has independently from Harvey, c. 1625, discovered the circulation of the blood, cannot be supported by Descartes' own works and wordings, c. 1632 in ON MAN.

Prof. Willem van Hoorn

Oegstgeest/Leiden

The Netherlands