Classicly

Poetry then is an imitation of nature, but the imagination and the passions are a part of man’s nature. We shape things according to our wishes and fancies, without poetry; but poetry is the most emphatical language that can be found for those creations of the mind ‘which ecstacy is very cunning in.’ Neither a mere description of natural objects, nor a mere delineation of natural feelings, however distinct or forcible, constitutes the ultimate end and aim of poetry, without the heightenings of the imagination.

The light of poetry is not only a direct but also a reflected light, that while it shews us the object, throws a sparkling radiance on all around it: the flame of the passions, communicated to the imagination, reveals to us, as with a flash of lightning, the inmost recesses of thought, and penetrates our whole being. Poetry represents forms chiefly as they suggest other forms; feelings, as they suggest forms or other feelings. Poetry puts a spirit of life and motion into the universe. It describes the flowing, not the fixed.