A French Roman Catholic theologian and philosopher. Arnauld was born in Paris into a family associated with Jansenism. Angelique Arnauld, his sister, was abbess of PORT-ROYAL, which became, under her direction, a center of Jansenism. One aspect of Jansenism is adherence to whatever view of the relation of divine grace to human freedom is expressed in Augustinus, a work written by Cornelius Jansen and published posthumously in 1640. Numerous Roman Catholics, including various popes, believed that the Jansenist account of grace is incompatible with the Roman Catholic dogma that divine grace can always be resisted by a free agent. Much of Arnauld's theological writings is devoted to a defense of the Jansenist account of divine grace and the claim that it is consistent with Roman Catholic dogma. Another important segment of Arnauld's theological writings concerns the role of the sacraments in the process of absolution, where Arnauld emphasized the attitude that the penitent must bring to the process if the sacrament is to absolve.

In connection with a school associated with Port-Royal Arnauld wrote or co-wrote three important textbooks that influenced seventeenth-century thought: Grammaire générale et raisonnée (1660), La Logique, ou l'art de penser (1662) and Nouveaux éléments de géométrie (1667).

In his Jansenist phase Arnauld offered and argued in favor of an historical approach to theology on the ground that the essential theological truths could be extracted from the work of the Fathers of the Church and, in particular, at least with respect to matters of divine grace and freedom, from the work of Augustine. He, therefore, strongly opposed what he took to be the innovative, speculative philosophical theology of LEIBNIZ and MALEBRANCHE. Criticism of Malebranche generated the majority of Arnauld's positive contributions to philosophy.

While Arnauld was a conservative in theology, he believed that scholastic philosophy had been exposed as inadequate by the seventeenth-century scientific revolution and Cartesian mechanics (see descartes). In philosophy, Arnauld regarded himself as a Cartesian, specifically associating himself with Descartes's theses concerning the nature and origin of ideas, the idea of God, the distinction between the soul and the body, and the nature of MATTER. This may seem odd, given Arnauld's famous criticisms of Descartes's Meditations on First Philosophy, including a brilliant critique of Descartes's arguments intended to prove that the SOUL and body are distinct substances (see the extended essay on the mind/body problem), a critique of one of Descartes's arguments for the existence of God, a query concerning the possibility of avoiding circularity, given Descartes's way of establishing the principle of clear and distinct perception, and a criticism of Descartes's thesis that nothing occurs in the soul of which it is not conscious. Except for this last thesis, which Arnauld regarded as inessential to Descartes's program, his criticisms were aimed at Descartes's arguments, not the conclusions of those arguments.

Arnauld criticized some of Descartes's doctrines because of their theological implications. The majority of Arnauld's criticisms of Malebranche center on what he viewed as Malebranche's speculative and innovative contributions to theology. But in the process, Arnauld formulated a theory of perception, which he presented as a mere recasting of Descartes's theory, but which, in fact, involves many ideas original to Arnauld. Arnauld's theory of perception is contained in two works aimed at Malebranche: Des vraies et des fausses idées (1683) and Défense de M. Arnauld, contre la réponse au livre des vraies et des fausses idées (1684). In these works, Arnauld articulated and defended a subtle form of a direct realist position, based on an act theory of ideas, in which ideas are identified with representative acts of the mind rather than objects of the mind that serve as intermediaries between an act of the mind and the external reality thereby represented.