This book discusses Lucretius' refutation of Heraclitus, Empedocles, Anaxagoras and other, unnamed thinkers in De Rerum Natura 1, 635-920. Chapter 1 argues that in DRN I 635-920 Lucretius was following an Epicurean source, which in turn depended on Theophrastean doxography. Chapter 2 shows that books 14 and 15 of Epicurus' On Nature were not Lucretius' source-text. Chapter 3 discusses how lines 635-920 fit in the structure of book 1 and whether Lucretius' source is more likely to have been Epicurus himself or a neo-Epicurean. Chapter 4 focuses on Lucretius' own additions...