Lucretius' On the Nature of Things (De Rerum Natura in the original Latin) is a long philosophical poem that discusses important aspects of Epicurean thought. This is an especially valuable work for understanding Epicurean thought because the works of the earlier Epicureans (two centuries before Lucretius) survive only in fragmentary form and are often preserved in writings by their philosophical opponents. On the Nature of Things is an extraordinary poetical work, full of all kinds of puns, word play, and imagery. It is equally extraordinary as a philosophical work because it contains a range of rigorous arguments defending and explicating Epicurean doctrines.

On the Nature of Things serves as the basis for our understanding of Epicurean physics and cosmology. The world, according to Lucretius, is mortal and made up entirely of atoms and void. All physical things are created out of the chance conjunction of atoms; death is nothing besides the disjunction of these atoms. Unlike almost every other philosopher of the time, Lucretius argues against the existence of an immortal soul or a divine creator of the world. He also has a strong doctrine with respect to free will -- the very atoms which constitute the world have a will of their own as does everything else in the world.

Lucretius also explores the moral and political ramifications of these physical and cosmological views. Since there is no afterlife and death is nothing other than the dissolution of a conjunct of atoms, we have no reason to fear death and we also have no reason to fear gods who may punish us in the afterlife. Such ideas went against all religious beliefs of the time. It also follows that all we have is this life, so we should give pleasure its due -- again, an idea that is in stark contrast to the teachings of philosophers like the Stoics. While the Epicureans were not hedonists in the contemporary sense -- they argued for a hierarchy of pleasures and advocated only natural and necessary ones -- they did argue that happiness consisted in maximizing pleasure and minimizing pain. Lucretius also offers an account of the creation of society on the basis of these doctrines.

On the Nature of Things is, then, unique and remarkable for all kinds of reasons. First, arguably no other text from antiquity is as beautiful in terms of its poetry as it is rigorous in terms of its philosophy. Second, it contains complete explications of Epicurean doctrines as well as arguments in support of some of these claims. Lucretius also synthesizes the physical and cosmological arguments with the moral and political ones, showing how the moral and political views follow quite naturally from the physical and cosmological ones; in this he is also a systematic philosopher.