The allegory of the cave is about education, about leading the soul from darkness into light, by stages. The allegory begins with a prisoner chained in the cave, able only to see the shadows of people moving. He thinks that the shadows are reality. This is the stage of Imagination. When the prisoner is free and sees the people whose shadows he saw in the cave, he thinks they are real. He takes the objects of the physical world, like trees and chairs, as the ultimate reality, instead of poor copies of the ideal Forms of trees and chairs. This is the second stage, of Belief. When the prisoner sees the world outside the cave he enters the third state, that of Thought. He is aware of the world of Forms. He realizes that objects we perceive with our senses are but copies of the ideal abstract Forms. The fourth and final stage, the stage of the philosopher-king, is the recognition of the Form of Goodness, which, like the sun
giving the prisoner light to see all things, leads to understanding all Forms. This is the stage of Understanding, the ultimate goal of Plato's philosophy.