As is well known, Epicurus and his followers held that the universe was infinite and f that its two primary components, void and atoms, were each infinite. The void was infinite in extension, the atoms were infinite in number and their total was infinite also in extension. The chief Epicurean proofs of these infinities are found in Epicurus, Ad Herod. 41–2, and in Lucretius 1.951–1020. As far as I can see, both the commentators to these works and writers on Epicurean (...) physics in general have neglected to take into account some material pertinent to these proofs, material found in Aristotle and especially in his commentators Alexander of Aphrodisias, Themistius, Simplicius, and Philoponus. In this article I wish to compare this neglected information with the proofs of infinity found in Epicurus and Lucretius and to discuss their authorship. (shrink)