x

Thinking alphabet thoughts made me wonder: why do we solve (or fail to solve but maybe at least get partial credit) for x ? Wikipedia, relying on a celebrated 1928 study of mathematical notation, credits Descartes: “The modern tradition of using x to represent an unknown was introduced by Descartes in La Géométrie (1637).” Speculation abounds about Arabic and Greek sources and about why Descartes chose x : Why We Use “X” as the Unknown in Math (Gizmodo).

A strange confluence: when I asked Murray, a mathematician, about x, I mentioned that perhaps the names of the x and y axes are explained by y ’s following x in the alphabet. And it turns out that Descartes gave us the x axis. The y came later. And then I realized that axes is yet another heteronym.

My favorite x is an X, in Wallace Stevens’s poem “The Motive for Metaphor”: “The vital, arrogant, fatal, dominant X.” Yikes! That line makes me wonder how Wallace Stevens did in algebra class.

But seriously: the X of that poem names an ultimately unknowable reality that resists and exceeds the imagination. I think I should get at least partial credit for that last sentence.

Thanks to Murray for the Gizmodo article.