Plato lets Socrates describe a group of people who have lived chained to the wall of a cave all of their lives, facing a blank wall. The people watch shadows projected on the wall by things passing in front of a fire behind them, and begin to ascribe forms to these shadows. According to Plato’s Socrates, the shadows are as close as the prisoners get to viewing reality. He then explains how the philosopher is like a prisoner who is freed from the cave and comes to understand that the shadows on the wall do not make up reality at all, as he can perceive the true form of reality rather than the mere shadows seen by the prisoners.
The Allegory may be related to Plato’s Theory of Forms, according to which the “Forms” (or “Ideas“), and not the material world of change known to us through sensation, possess the highest and most fundamental kind of reality. Only knowledge of the Forms constitutes real knowledge. In addition, the Allegory of the Cave is an attempt to explain the philosopher’s place in society: to attempt to enlighten the “prisoners”.
Inside the cave: In Plato‘s fictional dialogue, Socrates begins by describing a scenario in which what people take to be real would in fact be an illusion. He asks Glaucon to imagine a cave inhabited by prisoners who have been chained and held immobile since childhood: not only are their arms and legs held in place, but their heads are also fixed, compelled to gaze at a wall in front of them. Behind the prisoners is an enormous fire, and between the fire and the prisoners is a raised walkway, along which people walk carrying things on their heads “including figures of men and animals made of wood, stone and other materials”. The prisoners watch the shadows cast by the men, not knowing they are shadows. There are also echoes off the wall from the noise produced from the walkway.
Socrates suggests the prisoners would take the shadows to be real things and the echoes to be real sounds, not just reflections of reality, since they are all they had ever seen or heard. They would praise as clever, whoever could best guess which shadow would come next, as someone who understood the nature of the world, and the whole of their society would depend on the shadows on the wall.
Release from the cave: Socrates then supposes that a prisoner is freed and permitted to stand up. If someone were to show him the things that had cast the shadows, he would not recognize them for what they were and could not name them; he would believe the shadows on the wall to be more real than what he sees.
“Suppose further,” Socrates says, “that the man was compelled to look at the fire: wouldn’t he be struck blind and try to turn his gaze back toward the shadows, as toward what he can see clearly and hold to be real? What if someone forcibly dragged such a man upward, out of the cave: wouldn’t the man be angry at the one doing this to him? And if dragged all the way out into the sunlight, wouldn’t he be distressed and unable to see “even one of the things now said to be true,” viz. the shadows on the wall (516a)?
After some time on the surface, however, the freed prisoner would acclimate. He would see more and more things around him, until he could look upon the Sun. He would understand that the Sun is the “source of the seasons and the years, and is the steward of all things in the visible place, and is in a certain way the cause of all those things he and his companions had been seeing” (516b–c). (See also Plato’s metaphor of the Sun, which occurs near the end of The Republic, Book VI)
Return to the cave: Socrates next asks Glaucon to consider the condition of this man. “Wouldn’t he remember his first home, what passed for wisdom there, and his fellow prisoners, and consider himself happy and them pitiable? And wouldn’t he disdain whatever honors, praises, and prizes were awarded there to the ones who guessed best which shadows followed which? Moreover, were he to return there, wouldn’t he be rather bad at their game, no longer being accustomed to the darkness? Wouldn’t it be said of him that he went up and came back with his eyes corrupted, and that it’s not even worth trying to go up? And if they were somehow able to get their hands on and kill the man who attempts to release and lead them up, wouldn’t they kill him?” (517a) The prisoners, ignorant of the world behind them, would see the freed man with his corrupted eyes and be afraid of anything but what they already know. Philosophers analyzing the allegory argue that the prisoners would ironically find the freed man stupid due to the current state of his eyes and temporarily not being able to see the shadows which are the world to the prisoners.
“the region revealed through sight”—the ordinary objects we see around us—”to the prison home, and the light of the fire in it to the power of the Sun. And in applying the going up and the seeing of what’s above to the soul’s journey to the intelligible place, you not mistake my expectation, since you desire to hear it. A god doubtless knows if it happens to be true. At all events, this is the way the phenomena look to me: in the region of the knowable the last thing to be seen, and that with considerable effort, is the idea of good; but once seen, it must be concluded that this is indeed the cause for all things of all that is right and beautiful—in the visible realm it gives birth to light and its sovereign; in the intelligible realm, itself sovereign, it provided truth and intelligence—and that the man who is going to act prudently in private or in public must see it” (517b–c).
After “returning from divine contemplations to human evils”, a man
“is graceless and looks quite ridiculous when—with his sight still dim and before he has gotten sufficiently accustomed to the surrounding darkness—he is compelled in courtrooms or elsewhere to contend about the shadows of justice or the representations of which they are the shadows, and to dispute about the way these things are understood by men who have never seen justice itself?” (517d–e)