Plato was the most distinguished disciple of Socrates. the 4th century BC to which he belonged was an age of inquiry and as such Plato’s chief interest was philosophical investigations which form the subject of his great works in form of dialogues. He wasn't a professed critic of literature and his critical observation isn't found in any single book. They lie scattered in seven of his dialogues, more particularly in the Jon, the symposium, the republic and the laws.
He was the first systematic critic who inquired into the nature of imagination literature and put forward theories which are both illuminating and provocative. He was himself a great poet and his dialogues are the classic works of the world literature having dramatic, lyrical and fictional elements.
He gives the theory of mimesis (imitation) The arts deal with illusion or they are imitation of an imitation,