  The centrality of substance for the continental rationalists is further borne out by the importance of that concept for Spinoza, especially within his Ethics. Spinoza devoted the entire first part of that work to a consideration of substance, or, as he also termed it “Deus sive Natura” (“God, in other words, Nature”). The remaining parts trace the consequences of his conception of substance for epistemology, psychology, physics, and ethics. While Spinoza’s account of substance is quite rightly regarded as a development and working-out of Descartes’s metaphysics, there are also (as with Descartes and Malebranche) considerable, and important, differences between the two. What is important for our present purposes, however, is that (as with Malebranche) Spinoza’s departures from Descartes are almost always the manifestation of a form of rationalism purer than Descartes’s own. Most radically, Spinoza replaced Descartes’s substance pluralism with a monistic account modelled on Cartesian extended substance. Just as, in some places, Descartes treats bodies as mere modes of a single extended substance, so, for Spinoza, all individuals—both bodies and minds—are modes of a single substance.