Argument is conclusive... but... it does not remove doubt, so that the mind may never rest in the sure knowledge of the truth, unless it finds it by the method of experiment. For if any man who never saw fire proved by satisfactory arguments that fire burns, his hearer's mind would never be satisfied, nor would he avoid the fire until he put his hand in it that he might learn by experiment what argument taught.

Cited in: Carol A. Dingle (2000) Memorable Quotations: Philosophers of Western Civilization. p. 21