Catholic Encyclopedia (1913)/Marin Mersenne
French theologian, philosopher, and mathematician; b. 8 September, 1588, near Oizé (now Department of Sarthe); d. 1 September, 1648 at Paris. He studied at Le Mans and at the Jesuit College of La Flèche, where a lifelong friendship with Descartes, his fellow student, originated. Mersenne entered the novitiate of the Minims at Nigeon near Paris (1611), was sent to Nevers as professor of philosophy (1614-1620), and returned to Paris. His first publications were theological and polemical studies against Atheism and Scepticism, but later, Mersenne devoted his time almost exclusively to science, making personal experimental researches, and publishing a number of works on mathematical sciences. His chief merit, however, is rather the encouragement which he gave to scientists of his time, the interest he took in their work, and the stimulating influence of his suggestions and questions. Gassendi and Galileo were among his friends; but, above all, Mersenne is known to-day as Descartes's friend and adviser. In fact, when Descartes began to lead a free and dissipated life, it was Mersenne who brought him back to more serious pursuits and directed him toward philosophy. In Paris, Mersenne was Descartes's assiduous correspondent, auxiliary, and representative, as well as his constant defender. The numerous and vehement attacks against the "Meditations" seem, for a moment, to have aroused Mersenne's suspicions; but Descartes's answers to his critics gave him full satisfaction as to his friend's orthodoxy and sincere Christian spirit. Mersenne asked that, after his death, an autopsy be made on his body, so as to serve to the last the interests of science.
Mersenne's works are: "Quæstiones celeberrimæ in Genesim" (Paris, 1623), against Atheists and Deists; a part only has been published, the rest being still in manuscript, as also a "Commentary on St. Matthew's Gospel"; "L'impiété des déistes et des plus subtils libertins découverte et réfutée par raisons de théologie et de philosophie" (Paris, 1624); "La vérité des sciences contre les sceptiques et les pyrrhoniens" (Paris, 1625); "Questions theólogiques, physiques, morales et mathématiques" (Paris, 1634); "Questions inouïes, ou récréations des savants" (Paris, 1634); "Les mécaniques de Galilée" (Paris, 1634), a translation from the Italian; "Harmonie universelle, contenant la théorie et la pratique de la musique" (Paris, 1936-7); "Nouvelles découvertes de Galilée", and "Nouvelles pensées de Galilée sur les mécaniques" (Paris, 1639), both translations; "Cogitata physico-mathematica" (Paris, 1644); "Euclidis elementorum libri, Apollonii Pergæ conica, Sereni de sectione coni, etc." (Paris, 1626), selections and translations of ancient mathematicians, published again later with notes and additions under the title, "Universæ geometriæ mixtæque mathematicæ synopsis" (Paris, 1644).
DE COSTE, Vie du R. P. Mersenne (Paris, 1649); POTÉ Eloge de Mersenne (Le Mans, 1816); BAILLET, Vie de Descartes (Paris, 1691); HAURÉAU, Histoire littéraire de Maine, I, 321.
C. A. DUBRAY