This book studies the structure and origins of De Rerum Natura (On the nature of things), the great first-century BC poem by Lucretius. By showing how he worked from the literary model set by the Greek poet Empedocles but under the philosophical inspiration of the Greek philosopher Epicurus, the book seeks to characterize Lucretius' unique poetic achivement. It is addressed to those interested both in Latin poetry and in ancient Greek and Roman philosophy.