“Therefore do not seek to understand in order to believe, but believe that thou mayest understand.”
Tractates on the Gospel of John; tractate XXIX on John 7:14-18, §6 A Select Library of the Nicene And Post-Nicene Fathers of the Christian Church Volume VII by St. Augustine, chapter VII (1888) as translated by Philip Schaff http://www.ccel.org/ccel/schaff/npnf107.iii.xxx.html.
Compare: Anselm of Canterbury: "Nor do I seek to understand that I may believe, but I believe that I may understand".
Original
Ergo noli quaerere intelligere ut credas, sed crede ut intelligas.
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Aurelius Augustinus 183
early Christian theologian and philosopher 354–430Related quotes

“Humanly, no one escapes the obligation to "believe in order to be able to understand"”
credo ut intelligam
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"A Half Life" (1990), pp. 302-303
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Context: There's something that remains barbarous in educated people, and lately I've more and more had the feeling that we are nonwondering primitives. And why is it that we no longer marvel at these technological miracles? They've become the external facts of every life. We've all been to the university, we've had introductory courses in everything, and therefore we have persuaded ourselves that if we had the time to apply ourselves to these scientific marvels, we would understand them. But of course that's an illusion. It couldn't happen. Even among people who have had careers in science. They know no more about how it all works than we do. So we are in the position of savage men who, however, have been educated into believing that they are capable of understanding everything. Not that we actually do understand, but that we have the capacity.

“We refuse to believe that which we don't understand.”
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“Men are most apt to believe what they least understand.”
Book III, Ch. 11. Of Cripples
Essais (1595), Bartlett's Familiar Quotations, 10th ed. (1919)

http://twitter.com/DavidShuster [citation needed]
On Twitter

Source: Culture and Value (1980), p. 53e