Plato's Allegory of the Cave

Plato's allegory of the cave is an allegory presented by the Greek philosopher Plato in his work Republic (514a–520a, Book VII) to compare "the effect of education (παιδεία) and the lack of it on our nature". 

It is written as a dialogue between Plato's brother Glaucon and his mentor Socrates and is narrated by the latter. The allegory is presented after the analogy of the Sun (508b–509c) and the analogy of the divided line (509d–511e).

In the allegory, Plato describes people who have spent their entire lives chained by their necks and ankles in front of an inner wall with a view of the empty outer wall of the cave. They observe the shadows projected onto the outer wall by objects carried behind the inner wall by people who are invisible to the chained “prisoners” and who walk along the inner wall with a fire behind them, creating the shadows on the inner wall in front of the prisoners. 

The shadows represent distorted and blurred copies of reality we can perceive through our senses, while the objects under the Sun represent the true forms of objects that we can only perceive through reason.