 So far we have focused on generalist replies to metaphysical arguments for particularism. Generalists are not without positive metaphysical arguments for their own views, though. Most notably, so-called “constitutivists” sometimes invoke premises about the metaphysics of rational agency to argue for generalism. Kantian constitutivists are the most influential and clear-cut instance of this style of argument. Christine Korsgaard, for example, argues that the categorical imperative is constitutive of rational agency (Korsgaard 2008, 2009). The rough idea is that the principles of practical reasons unify us as agents, and allow us to take control over our representations of the world and our movements (Korsgaard 2008: 9). Insofar as simply being a rational agent commits one to the relevant principle(s), this strategy for defending generalism is also meant to be especially effective at silencing sceptical challenges, e.g., classic “why be moral?” challenges. The thought is that the sceptic has no coherent perspective from which to reject the relevant principles.