A volatile series of presidential transitions has only intensified the century-long conflict between progressive defenders and conservative critics of the administrative state. Yet neither side has adequately confronted the fact that the growth of uncertainty and the corresponding spread of guidance–a kind of provisional “rule” that invites its own revision–mark a break in the development of the administrative state as significant as the rise of notice-and-comment rulemaking in the 1960s and 1970s. Whereas rulemaking corrected social shortsightedness by enlisting science in the service of lawful administration, guidance acknowledges that both science and law are in need of continual correction. Administrative law has the resources to ensure that the provisionality of guidance does not lead to the abuses that conservatives fear. But to deploy those resources–and to carry through the reforms of administrative organization that are their natural complement–progressives must rethink their commitments to judicial deference to administrative authority and administrative deference to presidential authority, commitments on which the progressive defense of the administrative state currently depends.