Unlike animal knowledge, mature human knowledge is not a natural phenomenon. This claim is defended by examining the concept of such knowledge and showing that it is best analysed in deontic terms. To be knowledgeable is to possess epistemic authority. Such authority is assessable in two dimensions. The first is contextually appropriate truth-reliability. The second is epistemic responsibility in three senses of “responsibility”: accountability, due diligence and liability to sanction. The fact that knowledge can be impugned by non-culpable unreliability shows that, with respect to loss of authority, liability is strict. This entails that mature human knowledge requires some degree of epistemic self-consciousness: in particular, the conceptual capacities for critically examining one's beliefs. Arguments advanced by Kornblith for the claim that there is a vicious regress involved in this requirement are shown to depend on under-described examples. When the examples are fleshed out, we see that the “critical reflection” requirement does not demand constant self-monitoring but only the capacity to recognize and respond to appropriate epistemic queries. Recognizing that the practice of justifying one's beliefs conforms to a default and query structure also dispels the illusion that insisting that epistemic subjects have some sense of their own epistemic powers involves an unpalatable form of epistemic circularity.