Descartes is traditionally described as the father of modern philosophy, but in one way this description is potentially misleading. Since the Enlightenment at least, one of the dominant characteristics of modern philosophy has been its secular tendency; in the philosophy of Hume and his French contemporaries, for instance, God is conspicuous by his absence except as a target of criticism. But Descartes cannot be said to have inaugurated this turn toward secularization; God plays an absolutely central role in his philosophy (Cottingham 2008, 289; cf. Williams 1978, 162). Unlike Spinoza, Descartes may not be a “God-intoxicated man,” but he goes further than most philosophers in exploring the wide-ranging implications of the divine attributes for first philosophy and the natural sciences. It is by an appeal to the divine attributes or perfections that Descartes not only bridges troublesome gaps in his epistemology but also lays the foundations for his mechanistic physics.

To say that Descartes accords divine attributes a principal place in his philosophy is to say that his God is very much the God of the philosophers deriving from the Greek tradition; in Pascal's words, he is not the God of Abraham, Isaac, and Jacob. Descartes’ God is indeed a being whose essence and existence can be known by the unaided light of nature. The point might seem too obvious to be worth stressing, were it not for the fact that Descartes’ most prominent disciple, Malebranche, regularly invokes properties of God that can be known only through revelation; thus, even in philosophical contexts Malebranche appeals to the Word or Second Person of the Trinity. In the Principles of Philosophy I.25, Descartes asserts that we ought to assent to the doctrines of revealed theology, such as the Trinity and Incarnation (AT VIIIA 14, CSM I 201), but when practicing first philosophy, he does not avail himself of such doctrines. Although Descartes is prepared to offer an account of transubstantiation on his principles, it is more characteristic of him to leave (revealed) theology to the theologians.