Malebranche entered the Parisian Oratory in 1660 and was ordained into the priesthood in 1664, the same year as he discovered Descartes’ work. Descartes’ philosophy, especially its mechanical approach to physics, appealed greatly to Malebranche: but, less satisfied with Descartes’ treatment of more spiritual and divine matters, he also turned back to his other great mentor, Saint Augustine. Over the next few years, he sought to effect a synthesis between Cartesianism and Augustinianism, which he unveiled in The Search after Truth (1674–75). Other works followed, including Treatise of Nature and Grace (1680), Treatise of Ethics (1684), and Dialogues on Metaphysics and on Religion (1688). Alongside his own works, Malebranche was also quick to enter into exchanges with other authors, sometimes constructive, but often descending into acrimonious polemic. There were important private correspondences with Dortous de Mairan and Leibniz; and public disputes with Simon Foucher, Pierre-Sylvain Régis, Louis de la Ville (pseudonym of Louis le Valois), Bernard de Fontenelle, François Lamy, and (most bitterly and extensively) Antoine Arnauld.

Philosophically, Malebranche agrees with Descartes about mind-body dualism and union, about the essences of matter and soul as extension and thought respectively, and about the importance of turning to the intellect rather than the senses or imagination in order to avoid error. However, whereas Descartes maintains that the existence of the external world can be philosophically demonstrated from the veracity of God, Malebranche claims that such an argument shows only that its existence is probable. To achieve certainty, we must to turn to faith. As for the workings of this world, although he shares Descartes’ passion for mechanism, Malebranche maintains that Descartes errs on a few of the details. Whereas Descartes treats rest as something positive, Malebranche regards it as merely the privation of motion, a difference that has knock-on consequences for their respective accounts of the laws of motion.