From Laugh While You Can, Kay Ryan:

At about nine months, a baby starts to laugh when something is suddenly taken away from her. One of a baby’s first games is peek-a-boo, where someone repeatedly disappears and reappears (the enjoyment of which is, incidentally, considered a key indicator of later language acquisition skills).... 

If this strikes you as nonsense, it is. Something nonsensical in the heart of poetry is the very reason why one can’t call poetry “useful.” Sense is useful; you can apply things that make sense to other circumstances; you can take something away. But nonsense you can only revisit; its satisfactions exist in it, and not in applications. This is why Auden and others can say with such confidence that poetry makes nothing happen. That’s the relief of it. And the reason why nothing can substitute for it.... 

Nonsense exists only in relation to sense. It uses the rules of sense but comes to different conclusions. What is it but nonsense that has taken the grave weight of Frost’s and Dickinson’s poems—the sensible, expressible weight of them: all that is new is soon lost; human grief finds no sympathy in nature—and has left them weightless? Because if these poems, or a Shakespeare sonnet or a dark sonnet by Donne, had not had their arguments undone somehow, they would indeed crash upon our heads like hammers.  

All feelings must go through the chillifier for us to feel them in that aesthetically thrilling way that we do in poetry. Poetry’s feelings are not human feelings; we know the difference. There is some deep exchange of heat for cool that I’m trying to get at, something that I see operating in nonsense and that I believe gives poetry much of its secret irresistibility and staying-power (we are not exhausted by it and must always revisit it).