 Section 3 discusses the most thorough reply to this question in the literature, that offered by Onora O’Neill. To anticipate briefly: The general problem hinted at by Kant’s metaphors—of reason’s experiment upon itself, or compelling itself to give testimony—is that of reason’s self-knowledge (cf. Axi f). Kant assumes that we have a capacity of reason; but “reason grants [respect] only to that which has been able to withstand its free and public examination” (Axi n). We cannot, therefore, dogmatically assert the authority of this capacity: “reason… has no dictatorial authority” (A738/B766). This point is especially compelling given how fallible reason has proven in metaphysics: “how little cause have we to place trust in our reason if in one of the most important parts of our desire for knowledge it does not merely forsake us but even entices us with delusions and in the end betrays us!” (Bxv). Kant’s question, then, is how we might defend reason from various doubts and  worries[15]  and how we might discipline it without begging questions— for instance, by invoking claims or premises that themselves are open to doubt (cf. O’Neill 1989: Ch. 1, 1992, 2004 &amp; 2015). This is then the central task of critique (cf. Bxxxv): reason’s self-reflexive examination of itself, which establishes its limits and its “common principle,” and vindicates its authority.