One and One — are One —

One and One — are One —
Two — be finished using —
Well enough for schools —
But for minor Choosing —

Life — just — Or Death —
Or the Everlasting —
More — would be too vast
For the Soul's Comprising —
                                                                F497 (1862)  J769


Scholar Gary Lee Stonum claims that some two hundred of Dickinson's poems include specific math references. In this poem, Dickinson uses mathematics as a clever entré
 to metaphysics.

She begins with the attention-grabbing assertion that one plus one equals one, dismissing one plus one equals two as school learning. She's finished with that sort of thinking. The next line, the last in the first stanza, is difficult. On her manuscript, Dickinson included "inner" as a variant for "minor" and this complicates interpretation. "Inner Choosing" would be the soul's choices. "Minor Choosing," on the other hand, suggests decisions about unimportant matters. However, I think that Dickinson decided to wield "minor" ironically: arithmetic is fine for schools but not for such "minor" matters as life or death or the everlasting.

Those three "ors" present difficulties. The first stanza uses "and" for an additive effect "Or" signals a selective effect. We can choose to focus just on life, or death or the everlasting. Dickinson seems to be instructing us not to contemplate, for example, how the first two add up to the third – which would be an interesting unity.
        Instead, we are to think of how each of those three concepts is a one-ness comprised of many individual ones as if they are fungible entities. Dickinson wrote a second variant word on the manuscript: "two" for "More." While "two" would make a nice wordplay with "too," "More" gives us the richer idea that anything more than one of her grand metaphysical trio would be "too vast" for our understanding.

         That "vast" warrants a bit of scrutiny, too. What could be vaster than Life, Death, and Eternity? Those concepts are plenty vast. But that's what Dickinson is getting at: they are so vast they could take over your life. That makes sense coming from a poet who recused herself from the world in order to contemplate, let's see … Life, Death, and the Everlasting. She eschewed marriage, child rearing, church attendance, social events, and travel. For a poet of the mind and soul, any of those would, added to contemplation of Life, Death, and the Everlasting, be simply too vast. 

(I conflate the three on purpose, despite my comments about the "ors." I think Dickinson intends for the reader to think about them both as a unity, a One-ness, as well as severally.)