Socrates and Plato sought knowledge for its own sake and were dedicated to its pursuit. As philosophers, they were deeply interested in the distinctions between objective and subjective realities; in effect, between scientifically-arrived at conclusions and those inferred from incomplete data. Such is the prism through which one reads Plato's "Allegory of a Cave." In this mock dialogue between Plato's mentor, Socrates and the character of Glaucon, Plato attempts to illustrate the manner in which "reality" is falsely perceived and the effects on the subconscious of sudden enlightenment through exposure to an objective reality. In other words, Plato is explaining through the use of metaphor the struggle for objective knowledge and how distinguishing what is real from what is only perceived to be real can create conflict within and among people.
In "The Allegory of the Cave," Plato uses the darkness and isolation of a cave as a metaphor for the closed mind. The prisoners believe only what they see, which are shadows cast upon a wall by the interaction of a fire behind them and walkway passing through the cave, between the prisoners and the fire. The fire casts shadows of who- or whatever crosses the walkway upon the wall, to which the prisoners are forced to stare. As "Socrates" explains to Glaucon, "To them [the prisoners], I said, the truth would be literally nothing but the shadows of the images."
The conflict in Plato's metaphor emerges when one of the prisoners is set free and dispatched into the bright sunlight. Leaving the darkness of the cave for the brightness outside, the prisoner experiences the physical pain that is normally associated with sudden exposure to the sun following a protracted period in the dark. Freed from the physical -- and, in Plato's metaphor, intellectual -- confines of the cave, the prisoner is exposed to objective reality: life as it is, and not as it appeared in the confined space where all of reality was defined by the shadows cast upon the cave's wall. The effect of this exposure to objective reality, as commonly occurs when individuals are disavowed of incorrect notions following exposure to scientific fact, is initially resistance to information that contradicts earlier preconceived notions of reality. Again, Plato explains this phenomenon as such:
"At first, when any of them is liberated and compelled to stand up and turn his neck around and walk and look towards the light, he will suffer sharp pains; the glare will distress him, and he will be unable to see the realities of which in his former state he had seen the shadows; and then conceive some one saying to him, that what he saw before was an illusion, but that now, when his approaching nearer to being and his eye is turned towards more real existence, he has a clearer vision . . ."
The prisoner's subsequent conflict with his fellow prisoners who have remained chained in the cave and whose "reality" remains confined to their interpretations of the shadows on the wall provides the allegory's most important point: that people remain resistant to objective facts when all they have known are subjective interpretations of reality. As Plato/Socrates suggests with respect to the prisoner's enlightenment upon release from the darkness of the cave:
"Last of he will be able to see the sun, and not mere reflections of him in the water, but he will see him in his own proper place, and not in another; and he will contemplate him as he is."