I argue that Aristotle thinks desire is what motivates all animal movement and human action. Reason never motivates us directly, but it can exert an influence on what we desire. I argue that whether reason successfully does so depends on our character states, and that this is one reason why Aristotle is correct to say that virtue makes the end (i.e., the object of desire) right. The object of rational desire is the good, and it is because we have character states of a certain kind that we find the ends that reason proposes to be good. So it is because we are virtuous or vicious that we desire what reason proposes. Since reason cannot motivate us directly, reason can only be practical by affecting our desires. Since reason only affects our desires insofar as we are virtuous or vicious, it is virtue and vice that make practical reason possible.