Normative powers without conventions

What exactly do we need to do in order to make a promise, or to exercise some other normative power? On a view relied on by many philosophers writing on promising, consent, and related phenomena, the answer is that we must communicate a suitable kind of intention. On this view, power-conferring principles assert that specific normative consequences, determined in part by the content of the communicated intention, attach to such communicative acts, and these principles need not be socially practised or accepted to be true. The paper offers a defense of this convention-independent view against the forceful challenge developed by Jed Lewinsohn in 'The "Natural Unintelligibility" of Normative Powers'. Lewinsohn appeals to action-theoretic considerations to show that the relevant type of communicative act could not be performed under conditions of rationality and full information, and that therefore promissory power and other normative powers require the existence of social rules conferring such powers. The defense of the view targeted by Lewinsohn turns partly on the exact content of plausible constraints on the intelligibility of actions done with a particular aim, and partly on the question just how the social acceptance of power-conferring rules should be thought to matter.