Titus Lucretius Carus (/ˈtaɪtəs luːˈkriːʃəs/ TY-təs loo-KREE-shəs, Latin: [ˈtɪ.tʊz lʊˈkreː.tɪ.ʊs ˈkaː.rʊs]; c. 99 – c. 55 BC) was a Roman poet and philosopher. His only known work is the philosophical poem De rerum natura, a didactic work about the tenets and philosophy of Epicureanism, and which usually is translated into English as On the Nature of Things and somewhat less often as On the nature of the universe. Lucretius has been credited with originating the concept of the three-age system that was formalised in 1836 by C. J. Thomsen.