Like Gassendi, Descartes belonged to the early-seventeenth-century community of natural philosophers committed to Galilean science and the mechanical philosophy. Educated by the Jesuits at La Flèche – where Mersenne was also a student from 1604 to about 1609 – Descartes qualified as a lawyer at the University of Poitiers in 1616, after which he served as an officer in the army of Prince Maurice of the Netherlands and then spent several years traveling in Europe. He had a significant encounter with Isaac Beeckman in 1619 and, like Gassendi, found contact with the Dutch schoolmaster extremely stimulating. Shortly after meeting Beeckman, Descartes dedicated himself to the pursuit of natural philosophy. He settled permanently in the Netherlands in 1629, remaining there until his final, fatal move to Sweden in the last year of his life. He corresponded frequently with Mersenne and many other natural philosophers, including Beeckman, Constantijn Huygens (father of the physicist Christiaan), William Cavendish, the brothers Jacques and Pierre DuPuy, Jean-Baptiste Morin, Gassendi, Hobbes, and Henry More. His letters contain a wealth of information about key issues in seventeenth-century natural philosophy.

Descartes published a number of important and widely read works in natural philosophy.