Appetite, as Spinoza makes clear, is nothing but our striving to persevere in our being, and this striving, “as related to the mind and body together, it is called appetite” (3P9S). As related to our body, therefore, our appetite is the striving to persevere in a given proportion of motion and rest. Spinoza refers to this striving as the “actual essence of the thing” (3P7), as opposed to the formal essence of the thing which is “the essence of each thing insofar as it exists and produces an effect, having no regard to its duration” (4Preface). The formal essence, or our proportion of motion and rest, is independent of its duration in the face of external objects, objects which could, if they caused our body to lose this proportion, kill the body (Note Spinoza’s claim, in the Short Treatise (I/53): ‘…if other bodies act on ours with such force that the proportion of motion and rest cannot remain 1 to 3 [for example], that is death, and a destruction of the soul…’). The formal essence of the body is the idea of the body as comprehended under the attribute of extension, in contrast to the actual essence of the body that has durational existence. Understood in the context of other bodies, that is actually rather than formally, our striving to maintain the proportion of motion and rest is a striving in the face of external differences (that is, other objects). One of the functions or effects of our appetites, therefore, is to select against excessive differences, to filter and navigate relations in order to ‘maintain the proportion of motion and rest’. Such a selection process is simply part and parcel of the striving to persevere in one’s own being with its proportion of motion and rest. God, on the other hand, as absolutely indeterminate, self-caused substance is the infinite enjoyment of existing that is the affirmation of all differences, or as what Deleuze refers to in Spinoza’s Ethics as the ‘logic of purely affirmative difference and without negation.’ Since God is not absolutely indeterminate substance in potentia, but in actu, and because God does not have to select against difference (i.e., there is nothing lacking in God), God is the most perfect being. Finite and determinate beings, however, must select against difference if they are to persevere in their being. This is its appetite, its proper goal and end. At the same time, however, it is not clear what differences we must select against, or how much we can endure and still persevere in our being in the face of differences. It is not known in advance what a body can do. Consequently, through processes of experimentation and learned association we can become more perfect; that is, the more difference we do not have to select against, the more perfect we become; and it is in this light that Spinoza argues, in 3P12, for the existence of ideas that “aid the body’s power of acting.” By arguing for the effectiveness of such ideas, Spinoza is not being inconsistent with his earlier claims that the “decisions of the mind are nothing but the appetites.” To the contrary, the decisions of the mind which aid the body’s acting by selecting against difference, or by reducing difference to a common, known form, is nothing but the appetite itself, or our striving to persevere in our being.