The eighth bolgia: from above, it blazes with flame — every flame a soul, a tongue of fire concealing the evil counselors within. As fireflies in summer fill a valley, so the flames fill the ditch below. One great flame, cloven at its tip, moves toward them. It contains two souls: Ulysses and Diomedes, together in punishment for the counsels they shared in life — the Trojan Horse, the theft of the Palladium, the ruse that drew Achilles from Deidamia. Virgil speaks to the flame, not Dante: the souls within are Greek and would disdain Italian speech.
The larger horn of the flame — Ulysses — speaks. He describes his last voyage: after Circe, after Ithaca, he could not stay. His love for Penelope, his duty to his son — neither was strong enough against the desire to know the world beyond. He gathered a small company of his oldest companions and they sailed west, then south, past the pillars of Hercules — which Hercules had set as the boundary of the known world, warning human beings not to pass — and out into the open ocean. For five months they sailed south, toward the stars of the other hemisphere, until they saw a mountain rising from the sea — immense, dark, distant: Mount Purgatory, as we know, though Ulysses does not. Before they could reach it, a whirlwind came from the mountain and spun the ship three times, then sank it. The sea closed over them.
The speech is the poem's most famous set piece: a story of heroic transgression, of the refusal to accept the limits of the human, of knowledge pursued past the boundary that wisdom sets. Dante admires it enormously — and condemns it. Ulysses is not in Hell for his curiosity but for his counsel: he persuaded good men to their deaths in the service of his own desire to know. The flame speaks and is silent.