The duality of the poetic faculty according to Shelley is that the poet is not only an aesthete and creator of beautiful art in words, but that the poetry has moved history forward, and has changed the world. This being said, the poet is an artist and a prophet. In Shelley's own words:
It awakens and enlarges the mind…by rendering it the receptacle of a thousand unapprehended combinations of thought. Poetry lifts the veil from the hidden beauty of the world, and makes familiar objects as if they were not familiar; it reproduces (recreates) all that it represents;
The language of poets marks the before unapprehended relations of things, and perpetuates their apprehension, until the words which represent them, become through time signs for portions or classes or thoughts instead of pictures of integral thoughts.
It purges from our inward sight the film of familiarity which obscures us from the wonder of our being. It compels us to feel that which we perceive, and to imagine that which we know. It creates anew the universe after it has been annihilated in our minds by the recurrence of impressions blunted by reiteration.