 Kant’s diagnosis is that all such doctrines fail to capture the practical function of reason because they are heteronomous. They deny the authority and efficacy of reason, either holding that reason can only recognize objective ends that exist independently of its operations, or claiming that reason can bind agents only with the help of inclination or interest. For Kant heteronomy is a form of moral skepticism, understood as skepticism about the power of reason to establish moral truths and their authority. On this reading, then, constructivism is part of Kant’s overall argument for grounding ethics in reason, against the skeptical view that there are no normative truths (Korsgaard 1996a; Stern 2013; Wallace 2012). Skepticism is avoided only if reason is accounted as autonomous, and its authority does not derive from anything outside it. Reason is autonomous if its authority rests on its proper activity, rather than being derived from elements of the world outside of reason. Thus, the norm governing the activity of reason must be internal to reason, rather than dependent on any given value, interest, or desire. That is to say that reason is a “self-legislative activity” (Kant G 4: §2), and its legislative activity is governed by a norm, which Kant calls the ‘Categorical Imperative.’ The Categorical Imperative expresses the autonomy of reason and is its governing principle. It is not a mere decision-procedure to determine what to do, but the ‘constitutive norm’ of reason, that is, the basic standard of rationality in thinking and acting (Rawls 1989: 498–506; Rawls 2000: 166, 240–244; Korsgaard 1996a: 36–37; O’Neill 1989b: 18–19, 59n, 128, 180; Bagnoli 2013b; Reath 2006: 221–222; Reath &amp; Timmermann 2010; Engstrom 2009: Chapter 5).