Mark Peters’s “The umpty-zillion pleasures and surprising history of indefinite hyperbolic numerals’’ (Ideas, July 17) reminded me of a conversation several years ago with my grandson Solomon, who was 4 at the time. He asked, “How big is a zillion?’’ I said it wasn’t any particular number, just a word we use for a really big one.

“But,’’ he asked, “how do you know that, if you keep counting, you won’t come to a zillion? If there are no people in the world someday, will there still be more numbers, even without people to count them?’’

This left me speechless. He had a sense that the numbers go on forever, and innocently raised serious philosophical questions about distinguishing between numbers and their names and about whether mathematics is invented or discovered.

Ethan Bolker, Newton Highlands

The writer is a retired professor of mathematics at the University of Massachusetts Boston.