A mathematician, a physicist, an engineer and a linguist are trying to decide if all odd numbers are prime.

The mathematician says “one's prime, 3's prime, 5's prime, 7's prime, 9's not prime, so no.”

The physicist says “one's prime, 3's prime, 5's prime, 7's prime, 9's not prime, but maybe that's experimental error.”

The engineer says “one's prime, 3's prime, 5's prime, 7's prime, 9's prime ...”

The linguist says “one's prime, 3's prime, 5's prime, 7's prime. Aha! We have a universal generalization. Nine doesn't seem to be prime, but it must be prime at some underlying level of representation.”

(Arnold Zwicky in his Presidential Address at the Linguistic Society of America, 1992)