In the Republic, Plato describes a scene in which people live in a dark cave. The only things they can see are the shadows of figures cast on a wall in the cave. The point of the description is that the people in the cave believe the shadows on the wall are real, when they are only shadows cast by figures. Further, the people on earth are like the people in the cave because the observable reality they see is only a reflection or shadow of Plato's world of ideal forms.