The formal modern definition of infinitesimals doesn't really require them to be "truly" infinitesimal. It's defined as a limit, which removes the spooky element from it.

It's pretty strange that he claims being self-taught in college math, but this is literally in the first chapter of a college math textbook (Grossman's Calculus).

The formal modern definition of infinitesimals doesn't really require them to be "truly" infinitesimal. It's defined as a limit, which removes the spooky element from it.

It's pretty strange that he claims being self-taught in college math, but this is literally in the first chapter of a college math textbook (Grossman's Calculus).