Descartes’ Correspondence

### 17-19 October, Institut de Mathématiques de Toulouse

**Wednesday 17 October** **(Bâtiment 1R2, salle Cavaillès-132)**

**17h-18h30:**** Erik-Jan Bos (Radboud University Nijmegen)**, *Recent Research into Descartes’ Life and Letters*

**Thursday 18 October** **(Bâtiment 1R2, salle Cavaillès-132)**

**9h-10h30:**** Roger Ariew ****(University of South Florida)**, *Ethics, as constructed by 17th century Cartesians, from Descartes’ Correspondence*

**10h45-12h15:**** Carla-Rita Palmerino ****(Radboud University Nijmegen)****, ***Descartes and the sunspot. On an interesting difference between the Latin and the French version of the Principia.*

**14h15-15h45:**** Theo Verbeek ****(Utrecht University)**, *Baillet et Legrand: Une biographie et une édition manquée*

**16h-17h30:**** Delphine Bellis ****(University of Montpellier)**, *Descartes, Boulliau, and Morin on Light*

**Friday 19 October** **(Bâtiment 1R2, salle Picard-129)**

**9h-10h30:**** Rudolph Rasch ****(Utrecht University)**, *Beeckman and Descartes: Who Is the Master and Who Is the Pupil?*

**10h45-12h15:**** Sébastien Maronne** **(University of Toulouse)**, *What is Cartesian geometry? On **Descartes’ mathematical Correspondence.*

**Contact: **E.-J. Bos**, **erik-jan.bos@xs4all.nl and S. Maronne, smaronne@math.univ-toulouse.fr

### Abstracts

**Wednesday 17 October (Bâtiment ****1R2, salle Cavaillès-132)**

**17h30-19h:**** Erik-Jan Bos (Radboud University Nijmegen)**, *Recent Research into Descartes’ Life and Letters*

I will critically assess the latest biography of Descartes, *The Young Descartes. Nobility, Rumor and War*, by Harold Cook (2018). Cook reproaches experts like Ariew and Verbeek for ignoring important sources, and I will investigate these claims. This gives me the opportunity to present recent research into the Descartes family line, and to look for a mysterious Descartes in Madrid who assisted in unmasking a spy at the French court. I will furthermore present a hitherto unknown notarial deed mentioning Descartes and Helena Jans, the mother of the philosopher’s daughter. I will however start with making sense of the so-called La Hire and Poirier lists of Descartes’ letters (see Introduction in AT I).

**Thursday 18 October (Bâtiment 1R2, salle Cavaillès-132)**

**9h-10h30:**** Roger Ariew (University of South Florida)**, *Ethics, as constructed by 17th century Cartesians, from Descartes’ Correspondence*

I would like to discuss some of Descartes’ letters to Christina, Elisabeth, and Chanut on ethics[1] (especially with regards to the concept of happiness), and what the Cartesians[2] make of these letters, in contrast with Late scholastic views on happiness[3].

**10h45-12h15:**** Carla-Rita Palmerino (Radboud University Nijmegen), ***Descartes and the sunspot. On an interesting difference between the Latin and the French version of the Principia.*

In a letter to Mersenne, dated 4 March 1630, Descartes observes in passing that the plane of rotation of the sunspots does not coincide with the ecliptic of the earth. In my lecture, I will shed light on this cursory remark, by referring to Galileo’s, Scheiner’s and Gassendi’s theories of the sunspots, which were all known to Descartes. I will moreover explain how Descartes’ letter can help make sense of a difference between the Latin version of the *Principia*, where Descartes claims that the motion of the sunspots does not differ from that of the planets, and the French version where this remark is deleted.

**14h15-15h45:**** Theo Verbeek (Utrecht University)**, *Baillet et Legrand: Une biographie et une édition manquée*

La *Vie de Monsieur Des-Cartes* (1691) d’Adrien Baillet est non seulement la première biographie sérieuse de Descartes mais aussi une source importante pour la correspondance. Pourtant les études critiques et historiques sur ce projet, initié d’ailleurs non pas par Baillet mais par un de ses amis, Jean-Baptiste Legrand, sont rares et en fait se limitent à un article de Sebba. Dans ma contribution je tâche de combler un peu cette lacune et de corriger quelques-unes des conclusions de Sebba dans le but de rendre possible une évaluation critique de Baillet comme source.

**16h-17h30:**** Delphine Bellis (University of Montpellier)**, *Descartes, Boulliau, and Morin on Light*

In this talk, I propose to show how Descartes was led to refine his theory of light, by confronting it with those of two of his contemporaries who appear in his correspondence: Ismaël Boulliau, author of *De natura lucis* (1638), and Jean-Baptiste Morin, a staunch Aristotelian who addressed numerous objections to Descartes’ *Dioptrique* in 1638. This will help shed light not only on the role of subtle matter in light propagation, but also on the relationship between geometrical and physical optics, and on the role of experience in optics.

**Friday 19 October (Bâtiment 1R2, salle Picard-129)**

**9h-10h30:**** Rudolph Rasch (Utrecht University)**, *Beeckman and Descartes: Who Is the Master and Who Is the Pupil?*

Descartes wrote his *Compendium Musicae* for Isaac Beeckman, by the end of 1618, when he was in Breda, while Beeckman was principal of the Latin school of Middelburg. Later on, in 1630, Descartes complained in letters to Beeckman and Mersenne that Beeckman was apparently trying to claim the contents of the *Compendium Musicae* for himself, that the text was a summary of his (Beeckman’s) ideas on music, not of those of Descartes. Beeckman has left a comprehensive Journal with his ideas and observations about a great many subjects, among them music. A comparison of his notes on music from the years 1614-1618 with the *Compendium Musicae* may shed light on the question to what extent Descartes was, in 1618, indeed simply restating ideas brought forward by Beeckman first or presenting original ideas instead, so that we can try to answer the question if his later complaints were justified or not.

**10h45-12h15:**** Sébastien Maronne** **(University of Toulouse)**, *What is Cartesian geometry? On Descartes’ mathematical Correspondence.*

If Descartes’ *Géométrie *has generated a tremendously abundant secondary literature by being studied from the perspective of its relationship with Cartesian method and metaphysics*, *the mathematical Correspondence has been much less examined. Yet, it displays problems and objects that escape the dominion of geometry instituted by Descartes in his *Géométrie *—at least, as it is interpreted by Cartesian scholars… Jules Vuillemin has for instance written about these foreign elements to geometry in his *Mathématiques et métaphysique chez Descartes *that Descartes “*traite avec mépris ces découvertes [et] les regarde comme de simples procédés que sa méthode récuse*.” The same goes for the Latin editions provided by Schooten whereas they offered the starting point in the reading and the practice of Cartesian Geometry to early modern mathematicians. In my talk, I will discuss Vuillemin’s thesis and will try to show that one discovers another Cartesian Geometry, when scrutinizing the mathematical Correspondence, that reveals itself quite different from the *Géométrie *of the *doxa.*

[1] T*o Christina*: 20 Nov. 1647; *To Elisabeth*: 4 Aug. 1645, 1 Sept. 1645, 15 Sept. 1645, 6 Oct. 1645, Jan. 1646, Oct. or Nov. 1646; *To Chanut*: 1 Feb. 1647, 6 June 1647.

[2] Jacques Du Roure, anonymous author of Descartes, *Ethica*, the pseudo Claude Ameline, Antoine Le Grand, Pierre Sylvain Régis.

[3] Eustachius a Sancto Paulo, Théophraste Bouju, René De Ceriziers, Claude Frassen, Antoine Goudin.