Plato's cave: why shadows fool us
The short answer
In Book VII of The Republic, Plato pictures prisoners chained in a cave who see only shadows thrown by a fire behind them, and take the shadows for the real things. A shadow's size depends on distance from the fire, so from the wall alone a small near thing cannot be told from a large far one. A freed prisoner climbs into the sunlight, learns to see the things themselves and at last the sun, but back in the cave he loses at judging shadows.
Chapters and transcript
- 0:00
Plato pictured prisoners chained in a cave since childhood, facing a wall.
In Book VII of The Republic, Plato asks us to picture human beings in an underground den, chained since childhood so that they can only look ahead at the wall.
- 0:07
All they ever see are shadows, thrown by a fire behind them.
Above and behind them a fire is blazing; they see only the shadows it throws on the opposite wall of the cave.
- 0:13
Men carry figures along a low wall between the fire and the prisoners.
Between the fire and the prisoners runs a raised way with a low wall, like a puppet screen, and men pass along it carrying vessels and figures of animals and men.
- 0:20
A shadow's size depends on its distance from the fire, not on the thing.
By similar triangles, a figure 0.3 m high, 2 m from the fire, throws a shadow 0.3 × 8 ÷ 2 = 1.2 m high on a wall 8 m away. The distances are an example; Plato gives none.
- 0:28
Carry the same figure one metre nearer the fire, and its shadow doubles.
At 1 m from the fire the same figure throws a 2.4 m shadow. From the wall alone, the prisoners cannot tell a small near thing from a large far one.
- 0:41
They name the shadows, and take them for the real things.
Talking among themselves, they would suppose that the names they give belong to what is actually before them; to them the truth would be nothing but the shadows of the images.
- 0:47
Honours go to whoever best predicts which shadow comes next.
They confer honours on whoever is quickest to observe the passing shadows, remembers which went before and which followed, and so best foresees the future.
- 0:53
One is freed and dragged up into the sunlight. At first he sees nothing.
One prisoner is freed and dragged up a steep and rugged ascent into the sun. His eyes are dazzled and at first he can see nothing of the realities.
- 1:01
First shadows, then reflections in water, then the things themselves.
He must grow used to the upper world: first he sees shadows best, next the reflections of men and other objects in the water, and then the objects themselves.
- 1:09
Then the moon and stars by night; last of all, the sun itself.
Then he gazes at the moon and the stars by night, and last of all he is able to see the sun itself, in its own place.
- 1:21
Back in the cave, his eyes full of darkness, he loses at judging shadows.
Returned to his old seat, his eyes are full of darkness, and in a contest of measuring the shadows against those who never left he would be ridiculous.
- 1:28
Up he went, they say, and down he came without his eyes.
Men would say of him that up he went and down he came without his eyes, and that it was better not even to think of ascending.
- 1:34
Whoever tried to lead them up, they would put to death.
And if anyone tried to free another and lead him up to the light, Plato writes, they would catch the offender and put him to death.
Sources
Every figure in the film comes from these. The animation is illustrative.