It was Plato who bridged the gap between poetry and philosophy; for, in his work, appearance, despised by his Eleatic and Sophist predecessors, became a reflected image of perfection. He sets poets the task of writing philosophically, not only in the sense of giving instruction, but in the sense of striving, by the imitation of appearance, to arrive at its true essence and to show its insufficiency measured by the beauty of the Idea. (...). Then, little by little, thinkers concerned with philosophical justification of the arts moved the Platonic Ideas or archetypes, from the supra-celestial realm to the soul, from the transcendent to the immanent world. The object which the artist imitated underwent a similar change, passing from the empirical world to the soul, for it was held that what the artist imitated could not be the real object - for, if it were, the work of art would not be more beautiful than the immediate object - but the image in his soul, which is nothing other than the immanent Idea (...).

Erich Auerbach