'T was the saying of an ancient sage (Gorgias Leontinus, apud Aristotle's "Rhetoric," lib. iii. c. 18), that humour was the only test of gravity, and gravity of humour. For a subject which would not bear raillery was suspicious; and a jest which would not bear a serious examination was certainly false wit.
Source: Essay on the Freedom of Wit and Humour, sect. 5.