Marin Mersenne, a French mathematician, philosopher, and scientist, was one of the most influential figures of the scientific and philosophical revolutions of the seventeenth century. Although he is remembered primarily for his relationship with René Descartes, he was a significant figure in his own right and also, through his immense correspondence, publications, and personal acquaintances, a key figure in coordinating and advancing the work of the new philosophers and scientists.

He was born at Oizé, France, and studied at Le Mans and later at the Jesuit college of La Flèche, from 1604 to 1609. (Descartes, eight years his junior, was there from 1604 to 1612, but their friendship began later, around 1623.) He next studied in Paris and then entered the pious and austere order of the Minims. After further theological studies Mersenne taught philosophy at a convent in Nevers until 1619, when he was sent back to Paris...