In The Republic, Plato uses an extended metaphor involving prisoners who can see nothing but shadows projected on the cavern wall. They know only blurry outlines of the true objects represented by the shadows, and they pride themselves on how well they can memorize and relate to the puppet shows performed by their captors. If anyone from the outside world were to come down to them and describe color, sunlight, and stars, the captors would sure think the visitor insane; and should a visitor free the captives, and try to lead them out of the cave into the open air, wouldn’t the captors be terrified by the blinding light, and prefer to stay in their caves? And isn’t it the obligation of everyone who has ever stepped out of that cave, to return to the rest of the prisoners, and try to drag others towards the light — kicking and screaming, if necessary?
But, whether true or false, my opinion is that in the world of knowledge the idea of good appears last of all, and is seen only with an effort; and, when seen, is also inferred to be the universal author of all things beautiful and right, parent of light and of the lord of light in this visible world, and the immediate source of reason and truth in the intellectual; and that this is the power upon which he who would act rationally, either in public or private life must have his eye fixed. —The Republic by Plato