In one of his most well-known texts, The Republic, Plato sets out to demonstrate how human perception exists without anyone being aware of the existence of Forms, and how true knowledge is only gained through philosophy. Any knowledge gained by the senses is not knowledge at all, but simply an opinion.

The Allegory

The Allegory of the Cave reads as a conversation between Socrates and Plato’s brother, Glaucon. In the dialogue, Socrates asks Glaucon to imagine a world where an illusion is perceived as reality. To fur-ther his point, he creates the following example:

There exists a cave where, inside, a group of prisoners has been locked up since birth. These prisoners cannot move. Their necks and legs are chained so that they can’t shift or turn around and they can only see what is in front of them: a stone wall. Behind and above the prisoners is a fire, and between the fire and the prisoners is a low wall where people walk, carrying objects on their heads. The light of the fire casts shadows of the objects onto the wall in front of the prisoners. These shadows are all the prisoners can see. The only sounds they hear are the echoes from the cave.

Now, because these prisoners have never been exposed to the actual objects and all their lives they have only witnessed the shadows, they mistake these shadows for reality. The echoes of the cave, to them, are noises created by the shadows. If a shadow of a book were to appear, for example, these prisoners would claim that they have seen a book. They are not saying this is a shadow of a book, because their reality doesn’t know shadows. Eventually, one of the prisoners would understand the nature of this world and would be able to guess what shadow would come next, which would lead to praise and recognition from the other prisoners. 

Now, let’s suppose one of the prisoners is set free. If a person were to show that prisoner an actual book, the prisoner would not be able to recognize it. To the prisoner, a book is the shadow that was cast on the wall. The illusion of a book seems more real than the book itself.

Socrates continues, pondering what would happen if that freed prisoner were to then turn toward the fire. The prisoner would surely turn away from so much light and turn back to the dark shadows, which he holds to be more real. Now, what if this was taken one step further, and the prisoner was forced to go outside? The prisoner would be angry, distressed, and unable to see the reality before him because he would be so blinded by the light.

Plato’s Allegory of the Cave in Popular Culture

If this story sounds vaguely familiar, that’s because you might have seen some variation of it before. The 1999 blockbuster movie The Matrix is loosely based on Plato’s Allegory of the Cava To quote Keanu Reeves’s character Neo, “Whoa.”

After a little while, however, the prisoner would adjust and understand that the reality in the cave was incorrect. He would look toward the sun and understand that this entity was what created seasons, years, and everything that was visible in this world (and was even the cause of what he and his fellow prisoners had been seeing in the cave to a certain extent). The prisoner would not look back at those days in the cave with fond memories, for he would now understand that his former perception was not actually reality. The freed prisoner then decides to return to the cave and set the others free. When the prisoner returns, he struggles to adjust to the darkness of the cave. The other prisoners find this behavior startling (for the darkness of the cave is still their only reality), and instead of offering praise, they find him to be stupid and will not believe what the freed prisoner has to say. The prisoners threaten to kill the freed prisoner if he sets them free.

What it Means

Plato compares the prisoners chained inside the cave to people that are unaware of his theory of Forms. People mistake the appearance of what is in front of them as reality and live in ignorance (and quite happily, for ignorance is all these people know). However, when parts of the truth start to emerge, it can be frightening and can make people want to turn back. If one does not turn away from the truth and continues to seek it, he will have a better understanding of the world around him (and will never be able to return to that state of ignorance). The freed prisoner represents the philosopher, seeking a greater truth outside of the perceived reality. 

According to Plato, when people use language, they are not naming physical objects that can be seen; rather, they are naming something that can’t be seen. These names correlate to things that can only be grasped in the mind. The prisoner believed that the shadow of a book was actually a book until he was finally able to turn around and see the truth. Now, replace the idea of a book with something more substantial, like the notion of justice. Plato’s theory of Forms is what allows people to finally turn around and discover the truth. In essence, knowledge gained through the senses and perception is not knowledge at all, but opinion. It is only through philosophical reasoning that one is able to pursue knowledge.