 Here is a first-pass thumbnail sketch of that explanation: We have to act, because anything we do will be an action. Chairs are to sit on, and so a chair you can’t sit on is defective; being something you can sit on is a constitutive standard for chairs. Likewise, there are constitutive standards for actions, in just that way; a would-be action that did not conform to them would also be defective. In Korsgaard’s view, the question of why an item should conform to the constitutive standards for its type ‘answers itself’ (Korsgaard 2008, p. 61). So if she can show that deploying reasons satisfying one or another requirement is a constitutive standard for action – and the requirements she is going to argue for are Kantian – that will amount to showing why you should act on reasons that satisfy those Kantian requirements. Before we proceed to that argument, notice that we are starting to see how the philosophical motivations of the work we are surveying differ from program to program; the contrast between psychologistic and anti-psychologistic agendas is not the only, or even the most important, dimension of variation.