This paper connects a stylistic hallmark of Marx's work—a dramatic antipathy to imitation and copying—to his rejection of the epistemology of likeness or “harmony” in French romantic social Utopian thought. A space of the common without social mimesis—not just representation and imitation but competitive appropriation, likeness-based equality, social unity, cultivated resemblance, and so on—is in some ways paradoxical. But Marx upholds a vision of the common as collision, foreshadowing Althusser's notion of aleatory materialism, through a discourse of the atom. He moves from atheistic Epicurean models of abstract individuality and opposition to false universalism, to Hegelian ideas of the disaggregated atoms of political class activity, to a rejection of Buonarroti's ambition to harness self-seeking atoms in the collectivity, to a championing of real rather than ideal collisions. Acutely aware of social mirroring processes in the paradigm of the fetishism of the commodity, Marx puts the Lucretian “uproari...