The firmest trace of the poet outside his own poem is a letter. In February 54 BCE Cicero wrote to his brother Quintus that the poems of Lucretius showed flashes of brilliance and real craftsmanship. Nearly everything else told about the man arrived later. Jerome, a Christian scholar writing some four centuries afterwards, recorded that a love potion drove him mad, that he wrote in the intervals of sanity, that he killed himself, and that Cicero corrected the poem for publication. Scholars treat the story as unreliable: it fits badly with the respect Virgil, Horace and Ovid paid him, and it suits early Christian hostility to a school that denied the gods any care for the world. His dates are uncertain and his birthplace is unknown. What survives is one poem, On the Nature of Things (De Rerum Natura), and the poem says what he stood for.
He wrote, by the poem's own account, in a troubled time for his country. Rome in those decades lived through civil war, mass executions and political murder. There the teaching of Epicurus, a Greek philosopher dead some two centuries, had found followers in the governing class: Atticus, Cicero's friend and banker; Cassius, later one of Caesar's assassins; Piso, Caesar's father-in-law. Epicurus offered a calm mind, reached by seeing that the gods do not meddle in the world and that death is not to be feared. Lucretius set out to put the whole of that teaching into Latin verse.
The claim at its centre can be said in five words: death is nothing to us. The mind, like everything else, is made of atoms — tiny bodies moving through empty space — and when the body dies they scatter, so nobody is left for anything to happen to. The third of the poem's six books piles up some thirty arguments for the mortality of the soul. The best known compares death with the time before birth: no one is troubled by the ages that passed before they existed, and the ages after death will be the same blank.
The medium was the difficulty. Epicurus wrote in Greek prose and was reported to distrust poetry, which stood at the centre of Greek schooling. Scholars still dispute whether Lucretius, writing philosophy in verse, was bending a rule of the school at all. Latin also lacked the words. Lucretius complained of the poverty of his native tongue and, instead of borrowing the Greek atomos, "uncuttable", made Latin do the work: primordia, "first things", and corpora prima, "first bodies". He justified the verse with a doctor's image — as physicians smear honey on the rim of a cup so that children will drink bitter wormwood, he coated a harsh doctrine in song. He claimed no new doctrine. He called himself a follower of Epicurus, moved by love rather than rivalry, and worked from Epicurus's own long treatise On Nature.
The poem outlived the school that produced it. Lactantius, a Christian writer of the early fourth century, drew on it while calling its author mad for denying that God governs the world. It circulated again after Poggio Bracciolini, a papal secretary, found a manuscript in 1417. Montaigne took arguments from its third book for his essay "That to Philosophize Is to Learn to Die". In the seventeenth century the French priest Pierre Gassendi drew on Lucretius and on Diogenes Laertius, the ancient biographer of the philosophers, to build an atomism compatible with Christianity, and turned it against Aristotelianism. Gassendi's atomism made room for later scientists, more in Britain than in France.