 A significant problem with this  line[10]  is that Spinoza uses manifestly active language to describe the doings of individuals. For example, IIId3 defines “affect” as “affections of the body by which the body's power of acting is increased or diminished, aided or restrained, and at the same time the idea of these affections” (emphasis added). And in IIIp6, on which the entire psychological theory of the second half of the Ethics depends, Spinoza claims that individual things strive to persevere in their being; his subsequent uses of the IIIp6 seem clearly to suggest that Spinoza intends this striving to be understood as an a active principle rather than a mere tendency. On the conception of individuals as ratios of motion and rest that simply happen to endure, none of this would make any sense at all.