It is very dark in the cave, and everything, including the face of the person next to them, is in deep shadows. It is never mentioned whether the people are happy or sad, or whether they speak to each other. It is assumed that they speak at least enough to put names to the shadows they see on the far wall. According to some, the chains that bind the prisoners represent human senses, and the cave and the way they see it represents human life. Behind them is a fire, and there are people moving around between the fire and the people that are chained, so that the shadows are cast on the back wall of the cave for the chained people to observe. The only bright spot in the cave is the fire, and the only things for the people to watch are the shadows. They cannot turn around and see the fire, since the chains prevent this.
The people have been in this cave since childhood, and know no other way. They assume that this is all there is to be seen in life, and they do not hunger for anything else or strive to learn more. They have never been in the outside world, nor do they know anyone that has been, and in all probability they are not even aware that there is a world outside of what they see. They have never questioned the idea that there might be more to their life than what they see in the cave.
According to Socrates this is the human condition. Humans are trapped by their senses into seeing only what they see, and not trying to exercise their minds or their eyes to see further and consider that there might be something else out there.
Socrates goes on to say that if someone were to let one of these people loose from the cave, and take them outside, the sun's light would blind them for quite a while. They would only be able to look at shadows for a long time. Eventually they could start looking at other things. Finally, that person would be able to look up toward the sun, and see the light that it brings down to the Earth. If the person was then returned to the cave, he would no longer be able to see in the dark because he was used to the brightness of the sun, and the other chained prisoners would ridicule him. He would seem to them to be blind, and stupid for trying to tell them that there is a world outside of what they know.
There are several lessons that can be drawn from this. Socrates has said that the 'good' is reached only with a great deal of difficulty, and is the last thing to be seen. The sun in the Allegory of the Cave represents the 'good', as it is the last thing that the man removed from the cave would be able to look at, and it is white, brilliant, and blinding. Good in its truest sense is thought to appear this way, as a blinding truth that is difficult to look at, but can be faced with perseverance.
It is also important to notice that the man who comes out of the cave is blinded by the light, and when he returns to the cave, he is blinded by the darkness. According to some that have studied this issue "this means that when someone appears to have trouble understanding something, it could mean that they've come from a better place (outside into the cave) or a worse one (from the cave to the outside).
Socrates is also talking about education in the allegory. He is trying to point out that education isn't necessarily trying to make people see something new, but rather to make them look at what they already see in a new way. This concept is also illustrated in some of Plato's other works. He takes the stand that the soul is immortal, and therefore it 'knows' all that there is to know. It cannot be taught anything, but it can remember something when shown it in the proper way. According to Plato, the proper way is in the light (the good). When something is brought into the light, someone will often remember it, now that they can see it clearly.
Although the people in the cave believe what they see to be real objects, those that do not dwell in the cave but live in the light know them to be just shadows. The people in the cave need to consider new ways to look at what they see, but they are not interested in learning. In this way, the man who has returned to the cave represents education. Education assumes that the sight is there, but the person is just looking the wrong way. The goal of the educator is to redirect that sight.
Part of education, however, is "the education of the soul toward enlightenment," which is allegedly what happens when someone actually becomes a philosopher. Then the philosopher must "go back into the cave" in a manner of speaking, by entering the everyday world of politics, greed, and power struggles. He must 'step down out of the light', meaning the good, and go back into the darkness of those that are not enlightened.
Socrates also talks of 'guardians' in the allegory. He uses the word 'guardian' to refer to those people who will one day be rulers of the city. He is concerned about the guardian's education in light of the fact that the man in the cave who was brought out into the light and then returned could not teach anything of the outside world to the people in the cave. They would not believe his accounts of the outside world, preferring to believe that what they saw on the cave wall was the only truth.
Socrates feared that the guardians might be raised to be the same way, where they believed only what was in front of them. He was troubled by the idea that no one might be willing to come to the point of being more enlightened, and if they did, they could not convince anyone else to come with them. In light of this worry, he came up with what would be necessary to stop this from happening.
As for the guardian's education, this is what Socrates proposed: basic education in poetry, music, physical training and mathematics and then two or three years of compulsive physical training. At this point, the students will be about twenty years old. From there, the best will be selected and go on to study another ten years in the mathematical sciences. After that, there will be another process of selection and the ones chosen will receive another five years of training in dialectic.
The final selection process will come after the dialectic training, and the chosen ones will go on to fifteen years of political training, so at the age of fifty, they will be ready to become rulers of the city. He then states that it would be necessary for a group of philosophers to "come to power in a city, send out all the citizens over the age of ten, and start that society over again."
The dialectic that is mentioned is a method previously discussed by Plato, whereby someone comes to an understanding of the forms and is able to use them. Although the dialectic is somewhat hard to define, it is a method of rational inquiry, and is dependent upon the making of a step-by-step argument. Each step is built on the acceptance or rejection of the argument before it.
There is some concern about why Plato seems to feel that the dialectic cannot be taught to anyone until they reach the age of thirty. If he found it so useful, why is he so cautious with it? The answer appears to be that he realizes that the dialectic can be dangerous. Some people do not feel that the dialectic is anything more than a young child saying "why" a lot, and this type of behavior is tiring and destructive, both philosophically and socially. It seems as though Plato is going to make sure that the guardians know how to correctly use the dialectic, and have a clear idea of philosophy, before he allows them to use the dialectic as a tool.
Although what Socrates discusses, about philosophers taking over a city, is not going to happen, he is trying to make a point. Just as the people chained in the cave won't believe the man who has returned from seeing the outside world and the sun, the adults in a town will not believe a philosopher who claims he has been…