What does it mean to argue that a society is unjust? To assign wrongdoing not to individual actions but to social structures, and not to outcomes but to the nature of the social fabric? This is the defining question that most contemporary critical theory fails to answer. The opening of A Theory of Injustice: The Grammar of Structural Critique examines four contenders: Rainer Forst's theory of discursive inequality, Axel Honneth's model of social pathologies, Nancy Fraser's critique of capitalist expropriation, and Judith Butler's notion of differential precarity. All subscribe to the problematic view that injustice is a disparity between haves and have-nots, a violation of our universal dignity, or a state of privation vis-à-vis an ideal condition of complete participation or recognition. Critical theory remains trapped in a social and normative ontology that can only see the relative standing of individuals vis-à-vis each other but not the features of their social interrelatedness. The second part develops this alternative through an unabashedly normative reading of Karl Marx. Societies are structurally unjust when their forms of dependency both generate and exploit social precarity, while the distinctive feature of the capitalist era is the harnessing of our freedom to the unprecedented expansion of such exploitable insecurity. Our societies are not unjust because they disrespect our humanity, but because they are predicated on the productive abuse of our sociality.