John Keats says

I find that I cannot exist without poetry -- without eternal poetry -- half the day will not do -- the whole of it -- I began with a little, but habit has made me a Leviathan -- I had become all in a Tremble from not having written any thing of late....

In Poetry I have a few Axioms, and you will see how far I am from their Centre. 1st I think Poetry should surprise by a fine excess and not by Singularity -- it should strike the Reader as a wording of his own highest thoughts, and appear almost a Remembrance -- 2nd Its touches of Beauty should never be half way therby making the reader breathless instead of content: the rise, the progress, the setting of imagery should like the Sun come natural natural too him -- shine over him and set soberly although in magnificence leaving him in the Luxury of twilight -- but it is easier to think what Poetry should be than to write it -- and this leads me on to another axiom. That if Poetry comes not as naturally as the Leaves to a tree it had better not come at all. 

We hate poetry that has a palpable design upon us -- and if we do not agree, seems to put its hand in its breeches pocket. Poetry should be great & unobtrusive, a thing which enters into one’s soul, and does not startle it or amaze it with itself but with its subject. -- How beautiful are the retired flowers! how would they lose their beauty were they to throng into the highway crying out, ‘admire me I am a violet! dote upon me I am a primrose! Modern poets differ from the Elizabethans in this.  Each of the moderns like an Elector of Hanover governs his petty state, & knows how many straws are swept daily from the Causeways in all his dominions & has a continual itching that all the Housewives should have their coppers well scoured: the antients were Emperors of vast Provinces, they had only heard of the remote ones and scarcely cared to visit them.... Why should we be of the tribe of Manasseh when we can wander with Esau? why should we kick against the Pricks, when we can walk on Roses? Why should we be owls, when we can be Eagles?

I am certain of nothing but of the holiness of the Heart’s affections and the truth of Imagination -- What the imagination seizes as Beauty must be truth -- whether it existed before or not -- for I have the same Idea of all our Passions as of Love they are all in their sublime, creative of essential Beauty.... The Imagination may be compared to Adam’s dream -- he awoke and found it truth. I am the more zealous in this affair, because I have never yet been able to perceive how any thing can be known for truth by consequitive reasoning -- and yet it must be -- Can it be that even the greatest Philosopher ever arrived at his goal without putting aside numerous objections -- However it may be, O for a Life of Sensations rather than of Thoughts! It is ‘a Vision in the form of Youth’ a Shadow of reality to come -- and this consideration has further convinced me for it has come as auxiliary to another favorite Speculation of mine, that we shall enjoy ourselves here after by having what we called happiness on Earth repeated in a finer tone and so repeated -- And yet such a fate can only befall those who delight in sensation rather than hunger as you do after Truth -- Adam’s dream will do here and seems to be a conviction that Imagination and its empyreal reflection is the same as human Life and its spiritual repetition. But as I was saying -- the simple imaginative Mind may have its rewards in the repetion of its own silent Working coming continually on the spirit with a fine suddenness -- to compare great things with small -- have you never by being surprised with an old Melody -- in a delicious place -- by a delicious voice, felt over again your very speculations and surmises at the time it first operated on your soul -- do you not remember forming to yourself the singer’s face more beautiful that it was possible and yet with the elevation of the Moment you did not think so -- even then you were mounted on the Wings of Imagination so high -- that the Prototype must be here after -- that delicious face you will see -- What a time! I am continually running away from the subject -- sure this cannot be exactly the case with a complex Mind -- one that is imaginative and at the same time careful of its fruits -- who would exist partly on sensation partly on thought -- to whom it is necessary that years should bring the philosophic Mind.