The cave

Imagine, Socrates says, a long underground cave. At the back of the cave, a row of prisoners is chained — they have been chained from infancy — facing the back wall, unable to turn their heads. Behind them, higher up, a fire burns. Between the fire and the prisoners, a low wall runs across the cave; people walk past it carrying objects, statues, animals, instruments, and the firelight throws the shadows of these objects onto the back wall the prisoners face. The prisoners have seen nothing else their whole lives. They give names to the shadows. They believe the shadows are reality.

Now suppose, he continues, one prisoner is freed. He turns, and the firelight is painful — he has never seen anything so bright. The objects passing before the fire seem less real to him than the shadows he has known. He is told these are the real things, and the shadows were only their shapes; he is unconvinced. He is forcibly dragged up out of the cave, up the long passage to the surface — and the sunlight nearly blinds him. He cannot look at anything. Eventually his eyes adjust. He looks first at shadows on the ground, then at reflections in water, then at objects, and finally — last — at the sun itself. And he understands: the sun is what made everything else visible. The whole structure of the world above the cave is now clear to him.

Then he goes back. He has to. He is not allowed to remain in the sunlight; the philosopher's duty is to return to the cave and free the others. He goes back down. His eyes have to readjust to the dark. The prisoners think he has been ruined by his journey out — his vision is now worse than theirs. He tries to tell them what he has seen. They will not believe him. If he persists, Socrates says, they may kill him. The dialogue is twenty years from Socrates's own death by hemlock when he says this. Plato is not being subtle.