 Kant does not give a complete account of the relation of practical reason to theoretical reason in the Groundwork or any later works. However, the second Critique does include an important section that bears on this question: “On the primacy of pure practical reason in its connection with speculative reason” (5:119–121). (See Gardner 2006 and Willaschek 2010.) At the most general level, Kant’s notion of autonomy already implied some sort of primacy for pure practical reason. Against various stripes of rationalism, Kant denies that theoretical reason can have any insight into the supersensible. So reason has no possible access to a transcendent authority that could issue commands for thought or action. Against Hume, Kant denies normative authority to the inclinations. These points rule out the only ways that theoretical or instrumental reasoning could supply authoritative reasons to act. If there are such reasons—as the “fact of reason” pronounces —then only pure practical reason is left to supply them. Now, however, Kant argues that pure practical reason has “primacy” even on the home turf of theoretical reason. That is, pure practical reason should guide some of our beliefs, as well as our actions.