In Lucretius’ Trojan exemplum (1.471-477) the Ilioupersis is condensed in a powerful metaphorical conceit: love fire, glowing in silence in Paris’ heart, ignites the fiery war and becomes the real fire that kindles the flames that ultimately burn Troy. This scientific (or physiological) Lucretian metaphor, as well as the lexis and the imagery in this passage, have in fact a rather neglected tragic hypotext. This tragic background though (in particular, Ennius’ Alexander and Euripides’ Trojan trilogy) proves fundamental to interpret Lucretius’ literary examples; but it also appears to be extremely revealing to fathom the role of the poetry of the De rerum natura in Virgil’s Aeneid.