This article investigates why Lucretius does not dedicate any section of his poem to atomic size or provide a technical term to describe the concept. This absence is particularly significant because Epicurus’ Letter to Herodotus both uses the term μέγεθος to indicate atomic size and contains a passage reporting specifically on this property. First, the article argues that atomic size and shape are causally redundant in Epicurus’ ontology. Second, it demonstrates that the origin of both shape and size is found in the smallest magnitudes in Epicurean physics, the minima. Drawing on these findings, it concludes that, since atomic size violates the law of parsimony, it is a superfluous entity in the Epicurean system. After analysing passages from the De rerum natura, it suggests that the absence of atomic size in Lucretius may be deliberate. Lucretius’ microphysics works perfectly without introducing a philosophical notion of atomic size, and is more economical and efficient than that of Epicurus.

The revival of analytic metaphysics in the latter half of the twentieth century is typically understood as a consequence of the critiques of logical positivism, Quine's naturalization of ontology, Kripke's Naming and Necessity, clarifications of modal notions in logic, and the theoretical exploitation of possible worlds. However, this explanation overlooks the work of metaphysicians at the height of positivism and linguisticism that affected metaphysics of the late twentieth century. Donald C. Williams is one such philosopher. In this paper I explain how Williams's fundamental ontology and philosophy of time influenced in part the early formation of David Lewis's metaphysics. Thus, Williams played an important role in the revival of analytic metaphysics.