Poetry, even that of the loftiest, and seemingly, that of the wildest odes, [has] a logic of its own as severe as that of science; and more difficult, because more subtle, more complex, and dependent on more and more fugitive causes. In the truly great poets... there is a reason assignable, not only for every word, but for the position of every word.
I have said that poetry is the spontaneous overflow of powerful feelings: it takes its origin from emotion recollected in tranquillity: the emotion is contemplated till, by a species of reaction, the tranquillity gradually disappears, and an emotion, kindred to that which was before the subject of contemplation, is gradually produced, and does itself actually exist in the mind.
Good poetry could not have been otherwise written than it is. The first time you hear it, it sounds rather as if copied out of some invisible tablet in the Eternal mind than as if arbitrarily composed by the poet.