I have realized a few things:
"In his first paper on the Calculus (1669),
Newton proudly introduced the use of infinite series to expedite the
processes of the calculus...
As Newton, Leibnitz, the several Bernoullis, Euler, d'Alembert, Lagrange,
and other 18th-century men struggled with the strange problem of infinite
series and employed them in analysis, they perpetuated all sorts of
blunders, made false proofs, and drew incorrect conclusions; they even gave
arguments that now with hindsight we are obliged to call ludicrous."
-from "MATHEMATICS THE LOSS OF CERTAINTY" by Morris Kline, and
used in Don's book
As teachers we need to tell our students this often.
Sarah, age 7, unsolicited, said to Don: "At school when we do math
we use different methods that I am not used to. And they are hard. But if I
used my own methods it would be easy".
"You are a true artist- I know of no one who can help others learn like you do. Love, Mark"- That was from Don's middle son.
"The whole art of teaching is only the art of awakening the natural curosity of young minds." - Anatole France