Seated prisoners, chained so that they cannot move their heads, stare at a cave wall on which are projected images. These images are cast from carved figures illuminated by a fire and carried by people on a parapet above and behind the prisoners. A prisoner is loosed from his chains. First he sees the carved images and the fire. Then he is led out of the cave into ‘real’ world. Blinded by the light of the sun, he cannot look at the trees, rocks and animals around him, but instead looks at the shadows and reflections (in water) cast by those objects. As he becomes acclimatized, he turns his gaze to those objects and finally, fully acclimatized, he looks to the source of illumination, the sun itself.
Plato's Cave analogy can be used to illustrate the distinction between appearance and reality. In Plato's Cave, what visually appears to a prisoner is not what is real but rather an image or a shadow of what is real. For example, the prisoners in Plato's Cave have a visual appearance of the one who came back to tell them about the real world as shadowy black. But this is merely an appearance, since the released prisoner is not shadowy black. If this is correct, then one could make the following argument:
- We can distinguish between appearance and reality only if we can rule out the possibility that we are in Plato's Cave.
- We cannot rule out the possibility that we are in Plato's Cave.
- Therefore, we cannot distinguish between appearance and reality.