Hi there!

I’m afraid I can’t fully answer this question, as I simply do not know enough about the school at La Fleche to say with certainty what would or would not have been taught or referred to during Descartes’s time. What I can do is shed some light on Descartes himself.

The main point I want to flag is that the Council of Trent clearly had a large impact on Descartes, who seems to have consistently regarded it as authoritative. Here is an illustrative reference to it from the Fourth Replies, in which Descartes is responding to the objections raised by Arnauld to Descartes’s Meditations:

Now the teaching of the Church in the Council of Trent session 13, canons 2 and 4 is that ‘the whole substance of the bread is changed into the substance of the body of Our Lord Christ while the form of the bread remains unaltered’. Here I do not see what could be meant by the ‘form’ of the bread if not the surface that is common to the individual particles of the bread and the bodies which surround them. (AT 7:251)^1

This is illuminating for a couple reasons. First, Descartes is at pains to reconcile his own views with orthodox Catholic doctrine - Orthodoxy of which he takes the Council of Trent to be representative. Second, you can see here one of the key tensions in Descartes’s thought: The desire to reconcile his sincere Catholicism with the indebtedness of much Catholic thought to broadly Aristotelian ways of thinking. The Council’s intent was surely to make use of a broadly hylomorphic account of the Eucharist, to explain transubstantiation by way of understanding the substance as a composite of form and matter. But Descartes cannot accept this owing to his rejection of hylomorphism. Descartes simply does not think of bodies as composed of form and matter in the way Aristotle and the Schoolmen did. As such, he is forced, on pain of unorthodoxy, to give a rather implausible interpretation of the Council’s true intent in purely geometric terms, terms consistent with his own ideas regarding the nature of matter as mere extension (and indeed with his broad rejection of appeal to forms in general).

This tension comes up over and over again, perhaps most explicitly in the Dedicatory Letter to the Sorbonne (AT 7:1-6) that precedes the Meditations proper. Descartes is explicitly casting himself in the role of defender of the Catholic faith, positioning his philosophy as in harmony with Catholicism and indeed supportive of it. While there is a tendency in some recent literature^2 to downplay the religious motivations of Descartes’s work, this interpretation strikes me as reading back our own emphasis on science over religion onto Descartes. Descartes was a sincere Catholic who was interested in religion, religious philosophy, and establishing that his philosophy was in harmony with Catholicism. In short, I think we should take seriously Descartes’s proclamation at the conclusion of the Third Meditation that the contemplation of God constitutes “the greatest joy of which we are capable in this life.” (AT 7:52) Descartes was of course also interested in science, but he was also interested in religion for its own sake.

Anyways, back to the Council of Trent. Another informative reference to that Council comes in a letter Descartes sent to Mersenne in 1641 (AT 3:340), which refers to the aforecited reply to Arnauld. In this letter, Descartes refuses to send his comments on transubstantiation until he can consult the decrees of the Council of Trent. Again, Descartes here views that Council as the definitive authority on matters of doctrine. Elsewhere in the correspondence, however, Descartes expresses a more cynical attitude. Indeed, in his very next letter to Mersenne Descartes, while maintaining that he has managed to “reconcile” his views with those of the Church regarding transubstantiation, also vents some frustration at those who “confound Aristotle with the Bible and abuse the authority of the Church… I mean the people who had Galileo condemned.” (AT 3:349) Indeed, Descartes himself had refrained from publishing one of his physical treatises, The World in which he argues in favor of the new mechanistic science, after the condemnation of Galileo. The letter to Mersenne hints at why, while also reiterating that it is the Cartesian, not the Aristotelian, philosophy that best accords with the Catholic faith: “They would have had my views condemned likewise if they had the power… I am confident that… none of the tenets of their philosophy accords with the Faith so well as my doctrines.” (AT 3:350)

What emerges is a picture of Descartes, a sincere Catholic, trying to convince those around him of the truth of his philosophy, the new science, and of the harmony of his thought with Church doctrine. Aside from the Bible itself, St. Augustine, and St. Thomas Aquinas, the most frequently cited authority in the Cartesian corpus, at least so far as I can tell, is the Council of Trent. Indeed, in the English edition of the philosophical correspondence of Descartes, the Council of Trent is actually discussed the same number of times as Aquinas himself - At least if the index is to be trusted. But more than this, Descartes wanted to free Catholic theology from the “thrall of Aristotle” (AT 1:85). Sometimes this took the form of explicit engagement with the Council of Trent (or some other authoritative text) in an attempt to show that his philosophy did not conflict with (and indeed is the best way to make sense of and support) Catholicism. This is roughly the approach of the Meditations and of the accompanying Replies. Later, this approach would be tempered, in part out of respect for the Jesuits (here we see a connection to his education at Le Fleche) and in part in hopes that the success of his mechanistic science would eventually overturn the principles of Aristotle, catching the Schoolmen, as it were, unawares (AT 4:225). This is, I think, roughly the approach of the Principles.

To sum up, the Catholic doctrine embodied in the Council of Trent was regarded by Descartes as authoritative and exercised a non-trivial influence upon his thought. It is no great leap to suppose that this influence was due in no small part to the schooling he received at Le Fleche. Though whether and what other such texts he was exposed to at that school, I can’t say. But in any event, none seem to have exerted so strong an influence upon him as the Council of Trent.

Notes

1. Following standard practice, all translations of Descartes’s works are from The Philosophical Writings of Descartes. All citations of those works are to Oeuvres de Descartes.

2. For example,“There is… but one project in the Meditations, that of laying the metaphysical foundations of Descartes’s physics.” (Carrielo (1997), pp. 2)

Primary Sources

• Oeuvres de Descartes (1996). Edited by Charles Adam and Paul Tannery. 11 vols. Libraire Philosophique J. Vrin.

• The Philosophical Writings of Descartes (1984). Edited and translated by John Cottingham, Robert Stoothoff, Dugald Murdoch, and (vol. 3 only) Anthony Kenny. 3 vols. Cambridge University Press.

Secondary Sources / Further Reading

• Carriero, John (2008). Between Two Worlds: A Reading of Descartes’s Meditations. Princeton University Press.

• Gaukroger, Stephen (1997). Descartes: An Intellectual Biography. Clarendon Press.

• Kenny, Anthony (1968). Descartes: A Study of his Philosophy. Random House.

• Secada, Jorge (2000). Cartesian Metaphysics: The Scholastic Origins of Modern Philosophy. Cambridge University Press.

And as always in philosophy, the SEP is a phenomenal resource, as are the excellent bibliographies included with each article.