“Better to doubt methodically than to think capriciously.”

As quoted in Leaving Islam: Apostates Speak Out (2003) by Ibn Warraq, p. 68

Source: The Principles of State and Government in Islam (1961), Chapter 3: Government By Consent And Consent, p 50

Source: The History of Pendennis (1848-1850), Ch. 6.
Context: It is best to love wisely, no doubt; but to love foolishly is better than not to be able to love at all. Some of us can't: and are proud of our impotence, too.

Variously attributed to Lincoln, Elbert Hubbard, Mark Twain, Benjamin Franklin and Socrates
Misattributed
Variant: It is better to be silent and be thought a fool than to speak and remove all doubt.

Cited as an example of "What Mark Twain Didn't Say" in Mark Twain by Geoffrey C. Ward, et al.
Misattributed
Variant: It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt.

Introductory
The Grammar of Science (1900)

Source: The Rebel (1951), pp. 8 - 10 as quoted in Albert Camus and the Philosophy of the Absurd';(2002) by Avi Sagi, p. 44
Context: The absurd … is an experience to be lived through, a point of departure, the equivalent, in existence of Descartes' methodical doubt. Absurdism, like methodical doubt, has wiped the slate clean. It leaves us in a blind alley. But, like methodical doubt, it can, by returning upon itself, open up a new field of investigation, and in the process of reasoning then pursues the same course. I proclaim that I believe in nothing and that everything is absurd, but I cannot doubt the validity of my proclamation and I must at least believe in my protest. The first and only evidence that is supplied me, within the terms of the absurdist experience, is rebellion … Rebellion is born of the spectacle of irrationality, confronted with an unjust and incomprehensible condition.

In George R. R. Martin & Gardner Dozois (eds.) Rogues (p. 245)
Short fiction, A Year and a Day in Old Theradane (2014)

Source: The Second Sex