The proposition is a simple as the first verse of Genesis, and marginally more believable: in the beginning, Homer invented literature. He did so - if, that is, he was a single person - dualistically, in two poems that look ahead to different literary futures. The Iliad is our primordial epic, celebrating heroic violence and the glory of combat. The Odyssey, which begins when the war in Troy is over and follows its wily, wayward protagonist on his journey home to Ithaca, begets the alternative genre of romance, a form not end-stopped by death like the epic but open to accident and adventure, free to go on exploring indefinitely. Writers ever since have added footnotes to Homer, whether cynically summarising the Trojan War as a lecherous farce, like Shakespeare in Troilus and Cressida, or cramming Odyseus's decade-long tour of the Mediterranean into a single day in Dublin, as Joyce did in Ulyssses.