This may be the most widely known segment of Plato's writings. In the allegory of the cave, people are chained in place inside a dark cave, so that they cannot turn their heads and are forced to watch shadows projected on the cave wall. These shadows are cast by shapes which parade in front of a fire at the other end of the cave. This is a sort of archaic movie theater. The people imprisoned in the cave mistake the shadows for reality and invent fanciful theories for explaining the various types of shadows, discuss them, place bets on their appearances and movements and so forth.
If one of these captives were released, he could see the fire and the shapes parading before it. But further still, he could escape entirely from the cave and see the outer world. First, the outer world would have to be seen at night, the eyes not being adapted to the brightness of the day. Progressively, the released captive could see the outside world in full daylight and even make out the contours of the Sun itself. If now this adventurer were to return to the cave, the other captives would believe no part of his story. And if by malchance he would have become less interested in or less adept at speculating about the shadows on the wall, the other captives would take this to be the proof of actual madness. Such is the fate of seers.
This is a rather clear representation of the control system and scale of densities all in one concise package. Also the fate of the returning hero is clearly pointed out. Plato's freed captive corresponds in many points to the classic hero.
Plato may well have been an initiate of the mystery schools of his day, where such things were in all likelihood understood. We know very little of these mysteries but it would not be surprising to find these concepts there since these were certainly found in Gnosticism only a few centuries later. The mainstream of modern philosophy tends to see this allegory as simply a statement on intellectual knowledge and learning. This interpretation also works but it may be that Plato was referring to the 'matrix' in more literal terms.