Most philosophers think it uncontroversial that practical reason requires us to take the means to our ends, but have been silent about the normative foundation of this requirement. The interesting question, almost everyone agrees, is whether practical reason requires anything more, such as a principle of morality or prudence. This chapter examines the question what makes instrumental reason normative. It articulates the answers implicit in the rationalist and empiricist traditions, criticizing the former for its inability to explain how we can be motivated by the instrumental principle, and the latter for its inability to explain how we can be guided by it. It argues that the normativity of instrumental reason, like that of moral reason, must be grounded in the agent's autonomy, and also that there can be no requirement to take the means to our ends unless there are also required ends.
Keywords: autonomy, categorical imperative, desire, empiricist, Hume, instrumental, Kant, normativity, rationalist, reason