The sun, which provides the light in the mouth of the cave in the allegory of the cave, is recognized by the escaped prisoner as the source of the light that allows him to see the objects around him. The sun is like the Form of the Good, which is the source of all other Forms. If you know and understand the Form of the Good, then you will understand all the other forms. The sun, which leads the prisoner out of darkness, is like education, which leads the individual out of ignorance to understanding.