Unknown to the prisoners, this elevated causeway crosses through the cave. No one knows where it leads to. Unseen by the prisoners, life-sized two-dimensional cut -outs of various objects, like "trees", "girls" and "houses", are constantly being carried across this causeway. Because of the fire, shadows of them are projected on to the far wall of the cave. These shadows are what the wretched prisoners take to be real objects. They give names to them, and talk about them, because they know no better. In fact their "reality" is nothing but the shadow of a two-dimensional copy.