But wait!, there's more...

Already this semester I've had two 280 students ask me about the use of the word "but" in mathematical proofs. This is remarkable if only because none of the roughly 80 students I've had in this class in the past few years have ever asked about that word choice.

"I don't get it," one of the class's sharpshooters said this morning. " 'But' seems to have negative connotations. Why would you use that word?" She'd been puzzled by my writing something along the lines of "The lefthand side gives us blah blah blah...but this value is nothing other than..."

I had a hard time explaining it, and I hemmed and hawed. "It's like you're leading the reader to a surprise ending...or..."

"It sounds like an infomercial," one of the other students broke in, "You know, like 'but wait! There's more!' "

"Exactly!" I said. "That's exactly it! You're injecting a little bit of theater into the proof, indicating that you shouldn't be satisfied with what's already come, you're about to raise the stakes a bit and up the ante."

Only after a handful of jokes about Billy Mays doing mathematics were we able to continue.

I'm impressed with this group's acuity and attention to subtle details. The semester just keeps getting better and better.