Social and political concepts are indispensable yet historically and culturally variable in a way that poses a challenge: how can we reconcile confident commitment to them with awareness of their contingency? In this article, we argue that available responses to this problem—Foundationalism, Ironism, and Right Wittgensteinianism—are unsatisfactory. Instead, we draw on the work of Bernard Williams to tease out and develop a Left Wittgensteinian response. In present-day pluralistic and historically self-conscious societies, mere confidence in our concepts is not enough. For (...) modern individuals who are ineluctably aware of conceptual change, engaged concept-use requires reasonable confidence, and in the absence of rational foundations, the possibility of reasonable confidence is tied to the possibility of critically discriminating between conceptual practices worth endorsing and those worth rejecting. We show that Left Wittgensteinianism offers such a basis for critical discrimination through point-based explanations of conceptual practices which relate them to the needs of concept-users. We end by considering how Left Wittgensteinianism guides our understanding of how conceptual practices can be revised in the face of new needs. (shrink)