Plato allegory

1. In the allegory, Plato likens people untutored in the Theory of Forms to prisoners chained in a cave, unable to turn their heads. All they can see is the wall of the cave. Behind them burns a fire.  Between the fire and the prisoners there is a parapet, along which puppeteers can walk. The puppeteers, who are behind the prisoners, hold up puppets that cast shadows on the wall of the cave. The prisoners are unable to see these puppets, the real objects, that pass behind them. What the prisoners see and hear are shadows and echoes cast by objects that they do not see.
2. Such prisoners would mistake appearance for reality. They would think the things they see on the wall (the shadows) were real; they would know nothing of the real causes of the shadows.
3. So when the prisoners talk, what are they talking about? If an object a tree is carried past behind them, and it casts a shadow on the wall, and a prisoner says “I see a tree,” 
4. He thinks he is talking about a tree, but he is really talking about a shadow. But he uses the word “tree.”
5. Plato’s point is that the prisoners would be mistaken. For they would be taking the terms in their language to refer to the shadows that pass before their eyes, rather than (as is correct, in Plato’s view) to the real things that cast the shadows.
6. If a prisoner says “That’s a tree” he thinks that the word “tree” refers to the very thing he is looking at. But he would be wrong. He’s only looking at a shadow. The real referent of the word “tree” he cannot see. To see it, he would have to turn his head around.
7. Plato’s point: the general terms of our language are not “names” of the physical objects that we can see. They are actually names of things that we cannot see, things that we can only grasp with the mind.
8. When the prisoners are released, they can turn their heads and see the real objects. Then they realize their error. What can we do that is analogous to turning our heads and seeing the causes of the shadows? We can come to grasp the Forms with our minds.
9. Plato’s aim in the Republic is to describe what is necessary for us to achieve this reflective understanding. But even without it, it remains true that our very ability to think and to speak depends on the Forms. For the terms of the language we use get their meaning by “naming” the Forms that the objects we perceive participate in.
10. The prisoners may learn what a tree is by their experience with shadows of tree. But they would be mistaken if they thought that the word “tree” refers to something that any of them has ever seen.
11. Likewise, we may acquire concepts by our perceptual experience of physical objects. But we would be mistaken if we thought that the concepts that we grasp were on the same level as the things we perceive.

The prisoners live in a cave. The hole of the cave is facing outside’s sun. These prisoners who live in cave, their necks and legs are shackled by chains. The movement of their face is also restricted, therefore they can only face the wall of the cave in front of them. There is an enormous fire behind the prisoners, and between the fire and the prisoners is a walkway, along which people carrying artifacts. The shadows of these objects fall directly on the wall which is the sole view for the prisoners.  The prisoners would take these shadows to be real things and they would not know the real causes of the shadows.

Socrates supposes that a prisoner is released and get to see the real outside world. The prisoner stands up and walks towards the bright place. When the prisoner saw the fire, he feels glare because he only use to dim lights environment. Slowly, he gets accustomed to the existence of the new world. After some time, he would see more things around him and then discovers the true reality world.

The prisoner understands that the shadows on the cave’s wall are not real. Again assume that the prisoner have to return to the cave and make others aware of what he has discovered. The prisoner cannot adapt to the dark environment of the cave because he is no longer accustomed to the darkness. The others ridicule him blind and no one believes him.