Carl Andre and Richard Serra are major figures within the history of twentieth-century art, largely for their contribution to a newly won understanding of sculpture after modernism. This study argues, however, that we must look outside the discourse of modernism, and thus of minimalism and postminimalism, in order not only to understand just how deep Andre and Serra’s contributions run, but also to reconsider just what we believe those contributions to be in the first place. To that end, this study exchanges the categories of “art” in general and “sculpture” in particular for the concepts of “matter” and “material” as a means to look differently at the history of advanced art-making in New York circa 1968, the years of Andre’s floor works and Serra’s “props.” By tracking an underground strain of physicalist thinking in the historical discourse of minimalism, and by tracing the shifts in the scientific and philosophical understanding of the concept of matter in the wake of particle physics and the new atomic sciences of the middle of the Twentieth Century, this study seeks to answer how matter could come to be conceived of as a “readymade.” At the same time, through parallels to contemporaneous upheavals in the philosophy of science—in both its theories and practices—this study makes a case for understanding Andre and Serra’s contributions to the history of twentieth-century art according to a dialectic of reduction and emergence, and so offers a different set of concepts with which to tell the narrative of the art that comes after that which we call Modern.