by John Allen Paulos
Intelligibility or precision: to combine the two is impossible. ―Bertrand Russell.
Please forgive the long letter; I didn’t have time to write a short one. ―Blaise Pascal
I have always resonated with the two quotes above and believe they’re particularly germane to writing popular mathematics. Let me start with Russell. If his remark is taken literally, I would disagree with it, but if we take it merely as pointing out the often inevitable trade-off between precision and intelligibility, I find it rather profound. In my books I’ve certainly tried to be both precise and intelligible and hope that for the most part I have succeeded, as have so many other popular author of mathematics. The fact remains that combining the two is often a difficult task that at times depends on extra-mathematical understandings.
Take, for example, the notion of a continuous function in mathematics. Perhaps as a first approximation we might say that a function is continuous of we can graph it without lifting our pencil off the page. No breaks. This is intelligible, but is hardly precise and is, in fact, not what we mean by a continuous function. As generations of calculus students have understood (or misunderstood), the standard definition is simply not intuitive, involving as it does a complex statement involving the function in question and deltas and epsilons, Greek letters measuring distances along x- and y-axes. Unfortunately, immediately insisting on precision is a good way to discourage students from taking calculus. Read more »