De Rerum Natura (On the Nature of Things) is a remarkable philosophical poem in six books of Latin hexameters, composed by the poet Titus Lucretius Carus toward the middle of the first century BCE. (Lucretius lived from about 99 to about 55 BCE.) His poem is the fullest extant rendering of the ancient philosophy known as Epicureanism, after its founder, the Greek philosopher Epicurus, who lived in Athens in 341-270 BCE. Only fragments of Epicurus' own writing have survived.

Lucretius expounds "the nature of things," because Epicureans believed that the aim of life is to achieve a calm of mind they called ataraxia; that this calm can best be achieved by avoiding pain and extreme pleasure (which only leads to pain); that the greatest pleasure is intellectual; and that a proper intellectual grasp of the world involves a recognition that consciousness coexists with the body, because the opposite (belief in an afterlife for the soul) causes more pain than pleasure. Lucretius outlines a materialist physics to support these contentions: the universe is made up exclusively of either atoms or emptiness. ("Atom" is a Greek word used by Epicurus, following Democritus; Lucretius uses a Latin equivalent, primordium.) The gods, who are made of the smallest, swiftest, and finest atoms, exist in a state of perfect ataraxia, which prevents their having anything to do with human beings and the imperfect striving for pleasure in which human begins engage.

The selections included here are from the first three books. Lucretius makes clear the link, as he sees it, between understanding the material universe and calm of mind. Like stoics, Epicureans believed that one could do nothing about "the nature of things" because they are predetermined, but Epicureans believed that things are determined not by fate but by the movement of atoms, so Lucretius carefully explains how that movement happens, with an abundance of often ingenious examples (here omitted). Though his explanation falls well short of modern atomic physics, the conclusions he draws about the cosmos frequently coincide with modern understanding: that there are multiple worlds like ours, that motion is not toward the center (as Aristotle and Ptolemy argued), that the conditions that produced the earth are consistent throughout the universe. Lucretius' most famous passage is his argument in Book III that one need have no fear of death because the soul (or consciousness) is made of atoms and perishes with the body. This thought was a source of comfort to Epicureans, because it eliminated worry about the afterlife.

Because of its materialist assumptions, Epicureanism was roundly condemned during the Christian Middle Ages, and suspicion of Epicureanism remained firmly entrenched well into the seventeenth century, when the first English translations were made (one by the Puritan, Lucy Hutchinson). Montaigne knew De Rerum Natura well and quotes it often, but it is not clear that Shakespeare knew Lucretius' poem, and it is not clear either that he even knew Montaigne by 1599, the year he wrote Julius Caesar. Cassius identifies himself as an Epicurean in Plutarch's Life of Brutus, and the materialist explanation Cassius gives for the ghost that Brutus sees would have been enough, in itself, to allow Shakespeare to characterize Cassius's way of thinking as "Epicurean" in the way he does.

This text was prepared from the online version created for the Perseus project at Tufts University (, translated by William Ellery Leonard. Reformatted and reproduced here by permission.