In Plato's "Myth of the Cave," a man is portrayed who has spent his entire life in a cave chained by his hands, feet, and neck to the cave's wall. The man, along with several others chained with him, can see nothing but shadows being projected on the walls they face. In the Matrix, Thomas Anderson (a.k.a. Neo), the film's protagonist, lives in an illusory world, the Matrix. Neo, like the man chained to the wall in "Myth of the Cave," accepts as reality what he has seen his whole life. But both men are later and unexpectedly forced to question their perception of reality.
When the man in the cave is one day unchained and taken out of the cave into the light of outside, his eyes begin to burn from the brightness of daylight. Likewise, when Neo is taken out of the Matrix and brought into the real world, he asks Morpheus why his eyes hurt. "You've never used them before," Morpheus replies. The truth of reality is difficult for either man to accept immediately.
Before becoming completely attuned to their new atmosphere and knowledge, neither the man from the cave nor Neo is willing to accept the fact that what they have been introduced into is actually reality. But as each man spends more time exploring his new knowledge, he becomes increasingly determined to rescue those who are still in the dark. Because of this, the man from the cave returns to his former home in order to tell those still chained there of the outside. Neo also returns to the Matrix to inform its inhabitants of the real world. As a result, those who are afraid of the knowledge the man from the cave presents plot to kill him. Likewise, several people plot to kill Neo, who has been betrayed by Cypher out of his longing to return to the ignorance of the Matrix.