Principles of sufficiency are widely discussed in debates about distributive ethics. However, critics have argued that sufficiency principles are vulnerable to important objections. This article seeks to clarify the main claims of sufficiency principles and to examine whether they have something distinctive and plausible to offer. The article argues that sufficiency principles must claim that we have weighty reasons to secure enough and that once enough is secured the nature of our reasons to secure further benefits shifts. Having characterized sufficientarianism in this way, the article shows that the main objections to the view can be avoided; that we can examine the plausibility of sufficiency principles by appealing to certain reasons that support a shift; and that we should be optimistic about the prospects for sufficientarianism because many of our strongest reasons seem to be of this sort. This shift, I claim, is the overlooked grain of truth in sufficientarianism. © Cambridge University Press 2012.