Unfortunately, most mathematics texts teach only the mathematics, never the insights. I felt so frustrated by this gap that I wrote my own textbook, in which I try to teach both.
The story we ran on the topic at Mind Matters has gone viral via Slashdot, with five thousand views since yesterday afternoon. (A paper about CALCULUS?) Figures, Bartlett must have a point about the problem.
We usually think of basic mathematics such as introductory calculus to be fairly solid. However, recent research by UD authors shows that calculus notation needs a revision.