“By convention”

The previous post reminded me of something that happened in 7th grade pre-algebra:

Someone (perhaps me) asked the teacher one day why we used x to represent an unknown quantity.  Without hesitation, the teacher answered, "By convention."  He then moved on to solve 2x+6 = 16, or whatever the equation was we were working with.

At the time, I thought nothing of the response.  It wasn’t until years later, when I’d read all 399 of Isaac Asimov’s science essays from The Magazine of Fantasy and Science Fiction that I realized what a cop-out the answer was.  It was always possible to explain something clearly to a young audience, as Asimov had proved on a monthly basis for more than 30 years.  I grew visibly annoyed for several reasons:

  1. "By convention" while generally true, does not mean very much to a 7th grader.  Truth be told, I had no idea what "by convention" meant at the time.
  2. If I had know what it meant, I would have interpreted it as a synonym for "Because I said so."
  3. There are some fascinating reasons for why x is used, some of which are discussed in Unknown Quantity: A Real and Imaginary History of Algebra by John Derbyshire.

All my life I have been turned off by things that couldn’t be explained.  When I was young, I tended to ignore them.  As I grew older (and particularly after I read Asimov’s science essays), I began to embrace them and look for a better understanding of them.  It seems to me that my math teachers callous casting off of the question with "by convention" probably detracted from my early interest in math.  I wonder how much more interested I would have been if he had supplied a more reasonable answer.

About Jamie Todd Rubin

Jamie Todd Rubin writes fiction and nonfiction for a variety of publications including Analog, Clarkesworld, The Daily Beast, 99U, Daily Science Fiction, Lightspeed, InterGalactic Medicine Show, and several anthologies. He was featured in Lifehacker’s How I Work series. He has been blogging since 2005. By day, he manages software projects and occasionally writes code. He lives in Arlington, Virginia with his wife and three children. Find him on Twitter at @jamietr.