Lucretius' didactic poem De rerum natura ('On the Nature of Things') is an impassioned and visionary presentation of the materialist philosophy of Epicurus, and one of the most powerful poetic texts of antiquity. After its rediscovery in 1417 it became a controversial and seminal work in successive phases of literary history, the history of science, and the Enlightenment. In this 2007 Cambridge Companion experts in the history of literature, philosophy and science discuss the poem in its ancient contexts and in its reception both as a literary text and as a vehicle for progressive ideas. The Companion is designed both as an accessible handbook for the general reader who wishes to learn about Lucretius, and as a series of stimulating essays for students of classical antiquity and its reception. It is completely accessible to the reader who has only read Lucretius in translation.