Numerous individuals who extensively discuss René Descartes tend to focus mainly on his philosophical contributions and his often exaggerated claim to being the father of modern philosophy. Yet, he penned substantial works on a broad range of scientific subjects, such as mathematics, optics, physics, and astronomy. I have previously addressed his mathematics and optics, and will now shift my focus to his astronomy and physics.
The reasoning behind the tendency of those who enthusiastically write about Descartes’ philosophy to overlook his physics and astronomy, which were closely related, remains unclear to me. Perhaps it is due to what Knowles Middleton articulated in the previous episode’s quote: “René Descartes (1596–1650), a highly esteemed philosopher, whose ideas about physics have largely proven erroneous.” Or it could be attributed to the fact that Christiaan Huygens (1629–1695) and Isaac Newton (1642–1727) demonstrated their inaccuracies less than fifty years post-publication. This latter point would be incorrect, as Huygens identified as a Cartesian, while Newton initially viewed Descartes as a model during the development of his own physics and astronomy, only to later refute his theories throughout this process. It must also be noted that after the release of Newton’s Principia in 1687, the progression of physics and astronomy was characterized by an intense debate between the Cartesians and the Newtonians, a contention that persisted until the mid-eighteenth century.
After his initial encounter with Isaac Beeckman (1588–1637) while in the Netherlands training as a military engineer in 1618—during which Descartes became a staunch supporter of the corpuscular mechanical philosophy—he departed the Netherlands in 1619 to join the army of Maximilian I of Bavaria (1573–1651) to engage in the Thirty Years War. It was during this time in the winter of 1619 that he experienced his famed dream. From 1619 to 1620, he commenced writing the first iteration of his methodology, the Regulae ad directionem ingenii (Rules for the Direction of the Mind), a work he would continue to revise intermittently until 1628, but which was ultimately published posthumously in 1684.
From 1621 to 1625, Descartes wandered extensively, frequently returning to Paris where he sold an inherited property and invested the proceeds, securing a lifelong income. This period likely marked the beginning of his acquaintance with Marin Mersenne (1588–1648), who would serve as a significant sounding board throughout most of his life. Between 1625 and 1628, Descartes remained in Paris, developing his Regulae and his work on optics.
In 1629, Descartes made his way back to the Netherlands and initiated an ambitious philosophical scientific exploration of the universe, encompassing not just the Earth but the entire cosmos, aptly named Le monde, ou Traité de la lumière, which eventually appeared in posthumous publication in 1664.
He completed this extensive presentation of his philosophical and scientific ideas in 1633 and planned for its publication, when news arrived regarding Galileo’s trial and conviction for serious suspicion of heresy for violating the Church’s 1616 injunction “not to hold or teach the Copernican opinion,” essentially presenting the heliocentric theory as established fact. Descartes’ Le monde was heliocentric, prompting him to withdraw it from publication. Portions of this manuscript would eventually be published in Descartes’ Discours de la méthode, La Dioptrique, and Les Météores, all released collectively in 1637. The initial content of the original work is outlined as follows:
1. On the Distinction Between Our Sensations and the Causes That Produce Them
2. On the Composition of Heat and Light from Fire
3. On Hardness and Fluidity
4. On the Void and Our Sensory Awareness of Certain Bodies
5. On the Number of Elements and Their Properties
6. A Description of a New World and the Properties of Its Matter
7. On the Laws of Nature Governing This New World
8. On the Formation of the Sun and the Stars in the New World
9. On the Origin and Trajectory of Planets and Comets Generally; and Comets Specifically
10. On Planets in General, and Specifically on the Earth and the Moon
11. On Weight
12. On the Tides of the Sea
13. On Light
14. On the Characteristics of Light
15. That the Firmament of This New World Must Seem to