With renewed critical interest in capitalism, class analysis has returned to the intellectual agenda of social theory. Yet the enlivened debate about the significance of class has brought a familiar criticism, that of “class reductionism.” In this talk, McCarthy argues that class reductionism is best broken down into two analytically distinct components, what he terms the structural and political primacy of class. Structural primacy concerns the role of class structure in social explanation. Political primacy concerns the role played by class subjectivities in radical social transformation. This distinction allows us to identify four intellectual traditions with respect to the significance of class in social theory: relativism, constructivism, abstractionism and dynamism. The aim of this talk is not to defend Marxism against its detractors within this conceptual space. Instead, it is to differentiate class abstractionism and class dynamism as analytically coherent alternatives within Marxism, broadly construed. Through an engagement with recent theoretical contributions about class structure and class formation, McCarthy argues that class abstractionism reproduces weaknesses inherited from “orthodox” Marxism and offers an impoverished account of collective action. Such a view rests on an argument for the structural primacy of class that is unduly abstract and thereby assumes its political primacy in subjective terms. McCarthy instead sketches the contours of an alternative that is dynamic, conjunctural and explicitly attentive to the role played by non-class structures and subjectivities in processes of class formation.