[hzhou321]

Seems I agree with you (or you agree with mine) :)

I don't have problem with calculus -- or I wouldn't be able to do physics. I am having problem with calculus based on infinity.

> Also the idea of an actual infinity is a poetic mathematical one. It doesn't have to fit reality. The issue is whether it is useful and to what extent.

Well said.

> Also you don't differentiate numbers (real or rational), you can only differentiate functions.

Of course I meant distinction.