Authority is a normative power to create duties in others. The most plausible accounts of this general power relate it to existing reasons the subjects of authority have with which authoritative directives can help them comply. Such accounts lead some theorists to ascribe a morally ambitious function to political institutions. This article argues against such theories. It defends political authority as a modest normative power, constrained by the type of reasons with which it can help its subjects comply. This modest (...) account differs from other liberal views in the limits it imposes on the exercise of political authority. It casts doubt on familiar limits that protect an individual private sphere. Instead, it imposes a condition of moderation. It suggests that legitimate exercises of political authority should leave space for individuals to be motivated by reasons that political institutions do not and should not mediate for them. (shrink)