  Ultimately, though, Aristotle does come to the conclusion that there is a faculty of desire (orektikon) whose occupation it is to initiate animal motion. (Perhaps his initial reservations pertained only to one species of desire considered in isolation.) In any case, he says plainly: “It is manifest, therefore, that what is called desire is the sort of faculty in the soul which initiates movement” (De Anima iii 10, 433a31–b1). He understands this conclusion, however, in tandem with another which also serves as a qualification of his earlier finding that mind cannot be the source of motion. He holds, in fact, that it is reasonable to posit two faculties implicated in animal movement: desire and practical reason (De Anima iii 10, 433a17–19), though they do not work in isolation from one another. Rather, practical reason, broadly construed to incorporate the kind of image-processing present in non-human animals, is a source of movement when it focuses upon an object of desire as something desirable. So, practical reason and desire act corporately as the sources of purposive motion in all animals, both human and non-human (De Anima iii 10, 433a9–16), even though, ultimately, it is desire whose objects prick practical intellect and set it in motion (De Anima iii 10, 433a17–2). For this reason, Aristotle concludes, there is a faculty of desire whose activities and objects are primarily, if not autonomously or discretely, responsible for initiating end-directed motion in animals. What animals seek in action is some object of desire which is or seems to them to be good.