The Divided Line

In explaining the process of discovery of true knowledge, Plato introduces the metaphor of the divided line. The divided line has four segments which corresponds to four levels of knowledge and their respective objects of knowledge. Knowledge is an occasion from the lower aspects of the line to the highest, with rational insight being the HIGHEST LEVEL OF KNOWLEDGE that gives the true knowledge of IDEAS and the GOOD. At the lower two levels, it is not called KNOWLEDGE, but OPINION, as it depends on sensory experience.

Here, it is notable that the four levels of knowledge do not correspond to different realities, but are four different ways to comprehend the same object.

At the lowest level of the line (AB), the mind merely confronts images of Shadows of objects. The next stage of belief (BC) corresponds to plain sensory experience of things.

When a person moves from belief to thinking, he begins to enter into the realm of knowledge. At thinking (CD), he begins to enter into the realm of knowledge. At thinking (CD), he finds mathematical knowledge. However, the highest kind of knowledge is the knowledge gained by Rational Insight (DE), here he gets knowledge of objects as their true forms or ideas.

Based on observation of the sensory world, Plato realized that everything is in a state of flux ; nothing is absolute/immutable. Example : The food that nourishes today, may kill tomorrow as it decays.

From this realization, Plato concluded that there could be no definite knowledge based on sense observations. He thus believed in a transcendental world of eternity where ideas and forms exist. Since he believed the soul to be Immortal and Immutable, it belongs to the transcendental world in Plato’s Philosophy.

    To know is to be

Ultimately, knowledge of ideas is the highest knowledge (Divided line). However, is not enough just to know the truth, it is possible to become the truth. Plato’s theory of knowledge culminates into Metaphysics or Theory of Being, by “to know is to be be”(Similar to Advaita). One who knows Brahm, becomes Brahm.

The more you know, the closer to truth you are, the higher being you becomes. One who knows the truth of ideas/forms, becomes JUST and WISE, like the one who has escaped from the love cave and seen the world.

Love for the ultimate is the only way/ the force which leads to the ultimate truth, one who knows this, becomes the true being. For this, one must focus on the eternal, immutable ideas that are the source of all contingents in the world.


Analogy of Cave

Plato realizes that the general run of humankind can think and speak etc., without (so far as they acknowledge) any awareness of his realm of forms. The allegory of the cave is supposed to explain this.

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. Here is an illustration of Plato’s Cave:

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. So when the prisoners talk, what are they talking about? If an object (a book, let us say) is carried past behind them, and it casts a shadow on the wall, and a prisoner says “I see a book,” what is he talking about?

He thinks he is talking about a book, but he is really talking about a shadow. But he uses the word “book.” What does that refer to?

Plato gives his answer. The text here has puzzled many editors, and it has been frequently emended. The translation in Grube/Reeve gets the point correctly:
“And if they could talk to one another, don’t you think they’d suppose that the names they used applied to the things they see passing before them?”
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.
If a prisoner says “That’s a book” he thinks that the word “book” 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 “book” he cannot see. To see it, he would have to turn his head around.

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. 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.

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.

The prisoners may learn what a book is by their experience with shadows of books. But they would be mistaken if they thought that the word “book” refers to something that any of them has ever seen. 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.


Reminiscene/Recollection theory of knowledge (Epistemology)

Plato’s epistemology holds that ideas are not perception, that knowledge of Platonic Ideas is innate, so that learning is the development of ideas buried deep in the soul. In several dialogues by Plato, the character Socrates presents the view that each soul existed before birth with the form of the good and a perfect knowledge of ideas. Thus, when an idea is “learned” it is actually just “recalled”. According to Plato, the soul is immortal and its natural home is the transcendental world of ideas, where it first existed, without a body and in blissful contemplation of ideas.

However, when the soul sinks into a body, because the experience is traumatic, the soul forgets itself and its interests. Its knowledge of ideas is dimmed or blotted out by its immersion in the world of senses. Instead, in its confusion, it takes on the concerns of the body and in the process acquires the false beliefs that prevent one from making the right choices in life. It has to be reminded of the ideas that are already present in it.

This knowledge of reminiscence is possible through education. Everything is already present in the soul by birth. Education leads to merely the unfolding process of remembering everything. Knowledge is the recollection of the past. This gives rise to the doctrine of Apriori Knowledge of Descartes, Leibnitz.

    Relation between empirical World and world of ideas

In this regard, Plato propounds the following theories :

a) Copy Theory : Ideas are original archetypes. Worldly objects are their copies. In Platonic realism, forms/universals/ideas are related to particulars (instances of objects and properties) in that a particular is regarded as a copy of its form. For example, a particular apple is said to be a copy of the form of applehood and the apple’s redness is an instance of the form of Redness.

Criticism : If ideas are universal, and worldly objects are particular, then how can individual thing be a copy of something “universal”? Either both are particular, or both are universal.

Also, if worldly objects are mere copies, then the world becomes completely unreal. But according to Plato, the world is both real and unreal. Thus Copy theory cannot be valid.

b) Participation Theory : All the particular objects participate in the Universal or Idea. But no object can be said to fully participate in the idea. Particulars are said to participate in the forms, and the forms are said to inhere in the particulars. Example : Idea of Equality.

Criticism : If particular really participates in the universal, then the particular becomes real. Moroever, participation theory is vague. Particular objects are changeable, while ideas aren’t.


Arguments in favor of ideas

Plato’s theory of ideas can be understood from three perspectives :

a) Ontological : Ideas are things in themselves. They are the real entities, having an independent existence, depending neither on the world not God. They are non-spatial and non-temporal (i.e not belonging to this space and time)

b) Logical : Ideas are independent of sensuous experience. They are known through Reason of Rational Insight.

c) Teleogical : Ideas are purpose oriented. They are all directed towards the Idea of Good. Particulars exist to bring in actuality these ideas. The Idea of Good is beyond all ideas and rules and hence regulates them all.



– Beyond all ideas, but cause of all ideas too.
– Attracts all towards itself, like light attracts insects
– Ultimate reality/Highest Idea : Substratum of Universe, it occupies the same place as the God of Spinoza, Brahm in Advaita

Highest in the hierarchy of ideas, above even idea of god, absolutely free, self existent real. Everything in the world participates according to idea of good. It is the truth and beautiful. Purpose of human life is to realize the idea of good. Good brings teleological purpose to everything as the universe. It is the cause of the Universe. Indescribable as it is, not sensible.

Plato thus through this Idea of Good proposed longing and love for GOOD as the only way to attain the idea of good. This love is selfless and not directed towards any particular.

Now coming to the question in the topic, what all can be the arguments to justify Ideas/Universal? What all are the arguments that Plato gave? Well there are a few :

– Objects of this world are perishable and subject to change. Even empirical knowledge is subject to change. We can only opine about this world, but not gain universal, undoubted and unchangeable knowledge. This knowledge can be gained only of ideas, which have eternal existence.

– There are many particulars in this world, but they all have a common nature. Therefore, while particulars are many, their idea is one.

– Plato argues that we can understand the concepts of things which do not have existence anymore. Example : Dinosaurs, because their ideas are eternal. Plato uses metaphors/analogies to explain his theory of ideas such as analogy of cave, metaphor of equality.

Additionally, Plato propounds that ideas have a hierarchy from lower to highest ideas. The idea of good is the highest idea. All ideas are derived from the idea of good, but PLATO has not explained this further. This is the mystical aspect of his theory (This was later developed by Hegel, who explained how the absolute ideas unfolds through reason. The coming articles will deal with his philosophy in detail.)