Why the Traité de l'homme Was Not Published by Descartes

Descartes several times wrote that the aim of his philosophy was to provide an understanding of medicine so as to improve human life. Why, then, did he hold back his full views about the subject? Could they have been dangerous? Descartes composed a manuscript on human physiology but held it back. Only a few of his closest Dutch friends saw a copy of physiological manuscript of the early 1640s, and they kept it safe from public scrutiny, as he asked. Descartes continued working on the problems in it, making the text a mess that he could hardly read himself, as he told Mersenne in 1648. But a version, based on the manuscript circulated to his friends as edited by Florentius Schuyl, was later published in Latin (1662) as De homine; two years later an edition in French appeared, the Traité de l'Homme, overseen by Claude Clerselier. The text famously ends abruptly, with no discussion of the human soul. If we read Descartes's own views not as complete in the early 1630s but as evolving from the conversations of his youth - in the years before Galileo's condemnation - the later disputes in Utrecht, and his last work, Les Passions (1649), we can see how the agenda was set by materialist Epicureanism. Giving a full account of humanity without the need to explain the immortal soul would indeed have been dangerous; later commentaries in the published editions tried to remove the threat, but cannot be taken as Descartes's own opinion.