Human beings are famously prone to error, and proof-readers are, after all, only human. But who picks up the errors a proof-reader misses? John D. Barrow challenges readers to estimate the errors that aren't found from the errors that are.
To study a system, mathematicians begin by identifying its most crucial elements, and try to describe them in simple mathematical terms. As Phil Wilson tells us, this simplification is the essence of mathematical modelling.