Plato (427?-347 B.C.E.) is one of the giants of philosophy. Part of his accomplishment was to create a complete philosophical system, one whose parts — metaphysics, epistemology, ethics, political and social philosophy, etc. — were closely integrated. Some philosophers believe that much modern philosophy consists of a series of footnotes to Plato.
In Plato’s description of the Divided Line in Book 6 of The Republic, we see how closely his metaphysics and epistemology are related. (Search online for an illustration of the Divided Line.) According to Plato, reality has various levels. Corresponding to each level of reality is a level of knowledge. Plato (the main speaker in The Republic is actually Socrates, but most scholars think that Plato is actually expressing his own ideas) asks the reader to imagine a line and to divide it into two unequal parts. Then the reader is asked to take the two parts of the line and divide each of them into two unequal parts. Each of the parts of the line will correspond to different levels of reality, and knowledge of the different levels of reality will correspond to different levels of knowledge.
The first division that we make in the line corresponds to two different major levels of reality. There is the visible order of reality: We see the world we live in and also see images in mirrors and reflections on pools of water. Then there is the invisible order of reality: This is the realm of numbers, geometrical objects such as squares and triangles, and abstract concepts such as equality and justice. As we will see later, Plato believed that the invisible order of reality is more real than the visible order.
Each of the two orders of reality has been divided into two sections. This essay will describe Plato’s view of reality, beginning with what is less real and ending with what is most real.
The bottom half of the divided line is devoted to the visible order. The bottom half of the part of the divided line that is devoted to the visible order is the part of reality that consists of images. These images include shadows and reflections in water or on other surfaces — for example, a mirror.
All of these images are a very low order of reality. When we know about images, we have the degree of knowledge that Plato calls imagining. Images are less real than the objects that belong to the next level of reality.
The top half of the part of the line that is devoted to the visible order is the part of reality that consists of physical objects. These objects include animals, all plants, and the whole class of objects made by Humankind. In addition, these objects include individual trees and individual human beings.
All of these physical objects are still a very low order of reality, according to Plato. When we know about physical objects, we have the degree of knowledge that Plato calls belief. Physical objects are less real than the objects that belong to the next level of reality — the level of reality that is the bottom half of the level of reality known as the intelligible order.
The top half of the divided line is devoted to the intelligible order. The bottom half of the part of the divided line that is devoted to the intelligible order is the part of reality that consists of objects of geometry and kindred objects. These objects include triangles, squares, circles, and numbers. By a triangle, I don’t mean a triangle that is drawn on a chalkboard — I mean the geometrical object that is called a triangle. The triangle that is drawn on a chalkboard is not a perfect triangle — it does not have straight lines; a geometrical triangle (the triangle that you study in geometry class) is a perfect triangle and does have perfectly straight lines. Indeed, the triangle that is drawn on the chalkboard in a classroom is only an image of a real triangle — the perfect triangle with perfectly straight lines.
All of these geometrical objects are a high order of reality — but they are not the highest level. When we know about geometrical and mathematical objects, we have the degree of knowledge that Plato calls understanding. However, geometrical and mathematical objects are still less real than the objects that belong to the next level of reality.
To investigate the objects of geometry, we start with assumptions that are arbitrary starting points. People who study Euclid’s geometry will start by learning axioms — the assumptions of his geometry. If you reject Euclid’s axioms and come up with your own, you can establish a non-Euclidean geometry.
The top half of the part of the line that is devoted to the visible order is the part of reality that consists of the Forms or Ideas. The Forms are the highest form of reality. They are eternal and unchanging. Plato believed that there were many Forms. There is a Form for Tree, of which individual physical trees are only images. There is also a Form for Human Being and Forms for other physical objects. In addition, there are Forms for Beauty, Truth, Justice, Excellence, Piety, etc.
The Forms are the highest level of reality — they are what is most real — but the highest Form of all is the Form of the Good. When we know about the Forms, we have the degree of knowledge that Plato calls intelligence.
To investigate the Forms, we use dialectic. We start with an assumption, then subject the assumption to a rigorous process of analysis. This is what Socrates does in Platonic dialogue after Platonic dialogue. By investigating assumptions about the Form of Piety, we can acquire knowledge about the Form of Piety itself.
The Allegory of the Cave
One of the most famous allegories in Western civilization is Plato’s Allegory of the Cave, which also appears in The Republic — at the beginning of Book 7. The allegory represents Plato’s views about metaphysics and epistemology.
In the allegory, Plato asks us to imagine a strange scenario. A group of people has been kept imprisoned in a cave all their lives. They are tied up and are facing a wall. Behind the prisoners is a fire. Between the fire and the prisoners is a raised way on which a low wall has been built. People walk on the raised way, but they are hidden by the wall. However, they carry objects above them — statues of men and animals, etc. The shadows of these objects are cast in front of the prisoners.
All the prisoners have ever seen in their lives are these shadows, and this is what they think reality consists of. The prisoners have the degree of knowledge that Plato calls imagining, and the level of reality that they understand is that of images.
But suppose that a prisoner got free and turned and saw the raised way and the men walking along the raised way. This prisoner would have reached a higher level of understanding — that of belief. This prisoner would understand the level of reality that consists of physical objects.
Suppose further that the prisoner is taken outside of the cave. In the beginning, the light of the sun would hurt his eyes and he would not be able to see much. Plato writes that at first the man could most easily see shadows and the reflections of men and of other things that are reflected in water. In the allegory, these shadows and reflections correspond to geometrical and mathematical objects. When the prisoner reached an understanding of the shadows and reflections outside the cave, he would have reached the level of knowledge called understanding, and he would understand the level of reality that consists of geometrical and mathematical objects.
After a while, the prisoner’s eyes would grow accustomed to the light and he would then see the physical objects outside the cave: individual human beings, individual trees, etc. In the allegory, these physical objects outside the cave correspond to the Forms: the Form of Human Being, the Form of Tree, the Form of Piety, etc.
But later, the prisoner’s eyes would have grown so accustomed to the light that he could look at the Sun. In the allegory, the Sun represents the Form of the Good. When the prisoner is able to look at the Sun, he would understand the Form of the Good.
When the prisoner reached an understanding of the trees and human beings outside the cave, and of the Sun itself, he would have reached the level of knowledge called intelligence, and he would understand the level of reality that consists of the Forms, including the Form of the Good.
Back to the Cave
Suppose further that the prisoner returned to the cave and tried to tell the other prisoners what he had seen. He would be confused by the darkness of the cave, and the other prisoners would not believe his story. In addition, if the prisoner were to try to free the other prisoners and lead them out of the cave, the other prisoners would kill him. In Plato’s words, “If [the prisoners] could lay hands on the man who was trying to set them free and lead them up, they would kill him.”
Levels of Interpretation
The Allegory of the Cave can be interpreted in many ways. One interpretation is the one we have been looking at: The allegory explains Plato’s views on metaphysics and epistemology.
Another interpretation is that the allegory explains why Socrates was killed by his fellow Athenians. Socrates escaped from the cave, but returned to become a stinging fly to his fellow Athenians in an attempt to lead them out of the cave. The Athenians resented Socrates’ efforts and so killed him.
In addition, the allegory explains what philosophy is and what the philosopher does. The philosopher is attempting to get out of the cave by educating him- or herself about the various levels of reality — especially the highest level of reality: the Forms.
The Allegory of the Cave can also be interpreted as a criticism of our pre-philosophic lives. If all we are concerned about is the acquisition of money, then we are at the level of watching shadows on a wall.
Other interpretations exist, and more than one interpretation can be held simultaneously. The Allegory of the Cave is a work of high literary and philosophical merit, and as such, each generation of Humankind discovers that it says something to them.
Note: The quotations by Plato that appear in this essay are from his book Republic, translated by F. M. Cornford.
Copyright by Bruce D. Bruce; All Rights Reserved
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