Vijay Seshadri's "Imaginary Number"

I was pleasantly surprised when I heard last month that Vijay Sashadri won the Pulitzer Prize in Poetry for his book Three Sections. I have ordered the book and am waiting eagerly for it to arrive. In the meanwhile, I am reading some of his poems on the web. One poem that is included in Three Sections and was published a few years ago in Poetry, is "Imaginary Number." It reminds me of poems by Dickinson and Anna Swir, the ease with which they talked about the soul, as if it was their best friend out taking a walk or a child that was up to some mischief. "Imaginary Number" begins with a planetary devastation that leaves only a mountain standing, which therefore challenges the idea of comparisons--big/small, since the there is nothing to compare the mountain to, resulting in the soul feeling appeased. But the poet is not satisfied at voicing this profound philosophical truth that comparisons are relative, they create stress for human beings, and the disappearance of comparisons spells relief. The poet's insight occurs in the turn of the poem:

"The soul,

like the square root of minus 1,

is an impossibility that has its uses."

We are left contemplating the following questions: What is the square root of minus 1? Is the soul an impossibility? Is it an impossibility because it is intangible? Is the soul useless or useful? When does the soul become useful? What are the instances of its uselessness? 

 I like to think that poetry is refreshingly useless.  But poetry could have its uses--such as diverting you from suicide (as happens in The Hours when Laura upon reading Mrs. Dalloway changes her mind about committing suicide). The soul--unlike poetry--is intangible, impossible, has no this-ness, no substance, but keeps us together despite our near-devastating experience of being flung between our largeness and our smallness, between what-a-piece-of-work-is-man and a-tale-told-by-an-idiot-signifying-nothing.