Freud claimed that the concept of drive is "at once the most important and the most obscure element of psychological research." It is hard to think of a better proof of Freud's claim than the work of Nietzsche, which provides ample support for the idea that the drive concept is both tremendously important and terribly obscure. Although Nietzsche's accounts of agency and value everywhere appeal to drives, the concept has not been adequately explicated. I remedy this situation by providing an account of drives. I argue that Nietzschean drives are dispositions that generate evaluative orientations, in part by affecting perceptual saliences. In addition, I show that drive psychology has important implications for contemporary accounts of reflective agency. Contemporary philosophers often endorse a claim that has its origins in Locke and Kant: self-conscious agents are capable of reflecting on and thereby achieving a distance from their motives; therefore, these motives do not determine what the agent will do. Nietzsche's drive psychology shows that the inference in the preceding sentence is illegitimate. The drive psychology articulates a way in which motives can determine the agent's action by influencing the course of the agent's reflective deliberations. An agent who reflects on a motive and decides whether to act on it may, all the while, be surreptitiously guided by the very motive upon which he is reflecting. I show how this point complicates traditional models of the role of reflection in agency.