„Suppose you want to teach the "cat" concept to a very young child. Do you explain that a cat is a relatively small, primarily carnivorous mammal with retractible claws, a distinctive sonic output, etc.? I'll bet not. You probably show the kid a lot of different cats, saying "kitty" each time, until it gets the idea. To put it more generally, generalizations are best made by abstraction from experience. They should come one at a time; too many at once overload the circuits.“
— Ralph P. Boas Jr.
[Can We Make Mathematics Intelligible?, The American Mathematical Monthly, 88, 10, 1981, 727–731, 10.2307/2321471]