— Galileo Galilei Italian mathematician, physicist, philosopher and astronomer 1564 - 1642
Third letter on sunspots (December 1612) to Mark Wesler (1558 - 1614), as quoted in Discoveries and Opinions of Galileo (1957) by Stillman Drake, p. 134 - 135; Italian text online at Liber Liber http://www.liberliber.it/biblioteca/g/galilei/lettere/html/lett08c.htm, also from IntraText http://www.intratext.com/IXT/ITA0188/_PQ.HTM.
Variant translation: In questions of science the authority of a thousand is not worth the humble reasoning of a single individual.
As quoted in Biographies of Distinguished Scientific Men (1859) by François Arago, as translated by Baden Powell, Robert Grant, and William Fairbairn, p. 365
Variant: In the sciences, the authority of thousands of opinions is not worth as much as one tiny spark of reason in an individual man.
Context: for in the sciences the authority of thousands of opinions is not worth as much as one tiny spark of reason in an individual man. Besides, the modern observations deprive all former writers of any authority, since if they had seen what we see, they would have judged as we judge.