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.