Next, said I, here is a parable to illustrate the degrees in which our nature may be enlightened or unenlightened. Imagine the condition of men living in a sort of cavernous chamber underground, with an entrance open to the light and a long passage all down to the cave. Here they have been since childhood, chained by the leg and also by the neck, so that they cannot move and can only see what is in front of them, because the chains will not let them turn their heads. At some distance higher up is the light of a fire burning behind them; and between the prisoners and the fire is a track with a parapet built along it, like the screen at a puppet-show, which hides the performers while they show their puppets over the top.
I see, said he.
Now behind this parapet imagine persons carrying along various artificial objects, including figures of men and animals in wood or stone or other materials, which project above the parapet. Naturally, some of these persons will be talking, others silent.
It is a strange picture, he said, and a strange sort of prisoners.
Like ourselves, I replied; for in the first place prisoners so confined would have seen nothing of themselves or of one another, except the shadows thrown by the fire-light on the wall of the cave facing them, would they?
Not if all their lives they had been prevented from moving their heads.
And they would have seen as little of the objects carried past.
Of course.
Now, if they could talk to one another, would they not suppose that their words referred only to those passing shadows which they saw?
Necessarily.
And suppose their prison had an echo from the wall facing them? When one of the people crossing behind them spoke, they could only suppose that the sound came from the shadow passing before their eyes.
No doubt.
In every way, then, such prisoners would recognize as reality nothing but the shadows of those artificial objects.
Inevitably.
Now consider what would happen if their release from the chains and the healing of their unwisdom should come about in this way. Suppose one of them set free and forced suddenly to stand up, turn his head, and walk with eyes lifted to the light; all these movements would be painful, and he would be too dazzled to make out the objects whose shadows he had been used to see. What do you think he would say, if someone told him that what he had formerly seen was meaningless illusion, but now, being somewhat nearer to reality and turned towards more real objects, he was getting a truer view. Suppose further that he were shown the various objects being carried by and were made to say, in reply to questions, what each of them was. Would he not be perplexed and believe the objects now shown him to be not so real as what he formerly saw?
Yes, not nearly so real.
from THE ALLEGORY OF THE CAVE,
The Republic of Plato,
Francis Cornford, trans.