For a few months I've been writing with the principle that surprise is one of the most important elements of the line (see this previous post for more on the genesis of this idea). While I still think this is a point to keep in mind, I heard something the other day that made me think more deeply.
I was listening to a speech about the importance of wildness as an element of society (particularly with regards to coming-of-age rituals), and the speaker said something about the potency of wildness within boundaries, within constraints, and I thought, "But that's what poetry is--wildness within constraints." At least good poetry is, anyway.
It occurred to me that aiming for surprise in a line is a weaker version, a shadow, of aiming for the power of wildness within boundaries (think of the form of a coiled snake). Out-and-out wildness can devolve into chaos, but wildness within circumscribed boundaries perhaps comes nearer to the human condition than surprise itself does, without completely terrifying us the way that real chaos does.
And it seemed to me something to keep in mind with respect to writing poems, especially those about the chaos of our lives and emotions. Surprise is a good tool, yes, but it is only one shade of what we can do with the wildness within us.