Plato's Allegory of the Cave
source: Plato, Greek Philosopher, (427B.C. - 347 B.C.)
http://www.theweeklyinformant.com/platocave.htm
"Imagine men and women living as prisoners in an underground cave. These people have been here since birth, their bodies chained so that they cannot move. They can see only what is in front of them and can see no other prisoners.
"Behind the prisoners is a series of fires. Between the prisoners and the fires is a screen, like that at a puppet show. Behind this are people carrying various artificial objects, such as the figures of men and animals. The prisoners see nothing but the shadows of the objects cast by the firelight onto the cave wall in front of them. The cave has an echo so that the when the people in back of them speak the prisoners believe the sounds come from the shadow figures on the cave wall.
"Suppose one of the prisoners became free from his chains. The firelight would be painful to his eyes and the objects in back of him would so terrify him that he might desire to regain his former chained situation.
"If this free person actually crept out of the cave into the sunlight, he would be completely dazed, unable to comprehend ordinary objects. Slowly this former prisoner might begin to understand that it is the sun which is the source of light and life. He would feel sorrow for his former fellow prisoners. If he did return to his chains and speak to his fellow prisoners, they would think he was insane. And if they could lay hands on him they would kill him."