Explaining the world in which we live has been the essential pursuit of Philosophy since the beginning. Many have accounted for the world in different ways; from what substance everything is made being the usual quest. Plato’s “Divided Line” is one of the most studied and famous explanations of the world. It not only explains its essence, but the theory of knowledge according to Plato. This ideology is demonstrated through a line, which separates four metaphysical models of knowledge and the world. These models are not completely separate, but more of a ladder in which man must realize the next step of clarity by building off the last; the journey from ignorance to true knowledge.
Let us define the four different parts of the Divided Line. The line divides the world into two main fields; opinion and knowledge, or the visible and intelligible world, respectively. The visible world is perceived by the senses and subject to change. The intelligible world cannot be perceived by the senses, but only known and understood. This world is not subject to change, but rather is eternal and within it holds universal ideals. These two fields are then divided once more. Opinion is divided into perception (or illusion) and material objects. Knowledge, or the intelligible world, is divided into reasoning and understanding. Plato introduces this concept of the Divided Line in The Republic, where he uses his infamous Allegory of the Cave.
Plato explains a situation in which there are human beings, kept chained, facing a cave wall since childhood, who have never seen the light of the sun and cannot see each other. Between the people and the mouth of the cave is a fire, in front of which men pass carrying statues shaped like animals and other objects. The people in chains can only see the shadows cast from these objects. If one of the people were released and allowed to see the objects that had cast the shadows his whole life, he would now know a new level of what the objects he saw were. If he were to look at the fire itself, he would certainly be blinded momentarily, but once used to the light he would be able to understand that the fire was the source of the shadows. Thus moving from believing the shadows are reality, to believing the objects and fire casting the shadows are.
Imagine further that the man were to be let out of the cave all together. First he would be blinded, as with the fire inside the cave, and would take a while to acclimate to this new reality. After adjusting to such illumination, the man would be able to see clear objects of the world as reality. After this, the man would be able to look at the sun, and realize it is the source and reason for all he is seeing.
The life inside the cave represents Plato’s idea of the visible world. The shadows cast on the cave wall and the prisoners knowing only those shadows represents the majority of humans. Most people go through life only seeing imitations of the truth, or reflections, but not the real thing. The man set free to see the objects and fire causing the shadows transcends from the subset of illusion to the subset of beholding the material objects, while still residing in the visible world. The latter is a better cognitive state to be in, rather than merely seeing shadows of true objects. The progression from visible to intelligible world takes place when the man exits the cave and steps into blinding sunlight.
The intelligible world is that in which true understanding begins. The initial segment people enter into in the intelligible world is that of mathematical theory and reasoning. In this world, conclusions are made from axioms; only true conclusions and valid reasoning exists in this division of the intelligible world. This is where abstract and metaphysical theories would live. Ideas that are not physical, like a book or tree, but ideas such as the Pythagorean Theorem or the Quadratic Equation; something that holds true in any situation.
The fourth and final subset in Plato’s Divided Line is that of philosophical understanding. In this state there exists pure and absolute definitions, or Forms. In this state of philosophical understanding lie the universals, which is hinted at in the first subset of the intelligible world of mathematical reasoning. This state of understanding is concerned with the abstract Idea and Form of the entire world; the plan of nature as a whole, rather than specific objects or beings. Also in this category is Plato’s crucial idea of the Good.
Plato believed above all knowledge and understanding, the ultimate object of comprehension was the Good. He believed that through the Good everything gains worth. The Good is a very perplexing concept, and there is no one definition that all philosophers agree on. In attempt to erect something to work off of, however, we can see the Good as being that from which virtues derive. The chief virtues (wisdom, courage, temperance, and justice) come from the Good. The Good is not a Form or Idea in itself, however, which is what makes it so disconcerting. The Good transcends the Forms and Ideas; as stated before, it is through the Good that Forms and Ideas receive being. To put it in the context of Plato’s own allegory, the sun would represent the Good, as it is the source of illumination of true reality. Plato believed that humans naturally seek out the Good, and if one transcends from the bottom world of illusion to the world of philosophical reasoning, they can hope to attain a rational mind capable of grasping the Good.
Plato’s metaphysical and epistemological doctrines are difficult to completely separate. He explains the metaphysical, or the abstract concepts of being, knowing, etc., by asserting that they belong to the intelligible world rather than the visible. Plato believes the Good, which encompasses and truly gives being to the world lies beyond physical experience, which is demonstrated by separating it from the visible, perception-based experience, with his ‘line’. Of course, this is where it is difficult to keep his epistemology and metaphysics straight. Epistemologically speaking, Plato believes to know something is, in reality, a recollection of innate knowledge someone already has. The Divided Line shows that to reach the next cognitive state of the soul or being, a person must realize something new, that what they believed to be reality was, in fact, not true. One must recall the knowledge they have innately inside of them and realize that the new reality they find themselves in makes much more sense than the former. Another important distinction to make in terms of Plato’s epistemology is the difference between true knowledge and other thoughts mistaken for knowledge, such as opinions. Opinions are derived from the changing visible world, but Plato holds that knowledge is eternal. That being said, Plato believed that true knowledge could only be derived from the intelligible world, specifically the world of Forms.
The purpose of Plato’s Divided Line is to demonstrate the levels of knowledge a human can and should aspire to attain. He believed that the majority of people spend their lives living in the world of illusions, only seeing traces of truth in their lives. Humans desire the Good, and if they wish to attain it they must transcend from one world to the next, namely from the shadow world to the material world, from that to the world of mathematical reason, and finally to the world of the Forms. The intelligible world is the most difficult to grasp, but once it is grasped he who understands it would be appalled to think he ever knew anything else. In a sense, the Divided Line is a journey of no return. Once you know and understand the next world, you cannot revisit your earlier ignorance.