The question driving it is, not surprisingly, that of love. Unable to possess the object of desire, love wounds itself by itself. The poem begins with lived truth, that "Love appears/ as nothing when we begin to know it,/ nothing that is not its opposite, or/ whatever opposites mean, in this case--/ coming and ebbing, a kiss and heartache." By the end, however, the poem arrives at a philosophical understanding of what "nothing" consists of. "Nothing prevents/ nothing from passing through./ Nothing, after all, to try; nothing,/ after all, to do." To understand that understanding, substitute "love" for "nothing." They have become interchangeable, without loss.
The poem not only orchestrates its meditation, but it also presents images of great power. The crack recurs throughout the poem, as the arse-crack and cracks "rocketing" up a wall. What is fault and fracture becomes the beginning of a break in ordinary, rational consciousness, the satori of the poem's title, as in my favorite passage of the book:
What we talk about when we talk about loss
are the catastrophes: walls collapsing
and the terrible flood. What we forget is what
we fail to detect: the line opening like an eye
from one end of a dam to another;
a startled look and the averted vision
at a wrong word at yet another wrong time.
And so the need to look steadily at what is easily overlooked. The universe is looking back at us through the crack.