 Korsgaard’s case for constructivism parallels Kant’s argument for the autonomy of practical reason, as Rawls reconstructs it. It starts by objecting that substantive realism fails to respond to the skeptical challenge that there really are no reasons to be moral. This is because realism simply assumes the existence of objective standards for morality without offering a rational basis for them; hence the realist affirms what the skeptic denies. As a consequence, the realist also fails to show why we really ought to do as morality says, and thus fails as an account of the authority of moral obligations (Korsgaard 1996a; Korsgaard 2008: 30–31, 55–57, 67–68; Stern 2012a; Brady 2002). Realists presume that, in order to fend off skepticism, one has to anchor practical reasons in facts that are in themselves normative. But no appeal to such ‘normative facts’ can explain how they count as reasons and motivate rational agents. Suppose we agree that it is a normative fact that deception is morally wrong. How does awareness of this fact rationally compel us to refrain from deceiving? This is not only a psychological question about the impact that such a fact might have on our minds, but also, and most importantly, a normative question that concerns its authority.