Reasons derive their normativity from the fact that we are creatures who cannot escape reflecting and deliberating about what would be rational to believe or best to do. Therefore, we are susceptible to considerations speaking for or against the various options in believing and acting. We believe something to be the case because we have conclusive reasons for that belief, and we think that we must do something because reasons point out that this is the best or sole eligible option. In his Groundwork of the Metaphysics of Morals (1785/1996) Kant is mainly interested in analyzing and understanding the idea of being practically obliged by reasons. If reasons make it the case that something ‘ought’ to be done or must not be done, from where do these reasons derive their authority? Why are they good (or conclusive) reasons and why should we listen to them? Kant’s project is a search for the ultimate source of the normativity of practical reasons and thereby a search for the character of normativity in practical reasoning as such. Kant’s ethics may be seen as one long and expanded answer to the question ‘what does Sollen mean?’ 1