“If a man will begin with certainties, he shall end in doubts, but if he will be content to begin with doubts, he shall end in certainties.”

In context, I like it a lot. Religion, science and politics would all progress for the better with the quote's sentiment as a foundation.

Religious fundamentalists start with certainties and stay with certainties. Reason never enters their minds.

Very true, but a bit of a broad stroke, jim k, Austin. The best place to fool people starts from the pulpit. False confidence arises through cloaked uncertainty. 
"THROUGH DESIRE a man having separated himself seeketh and intermeddleth with all wisdom." Prov 18:1
To be content when in doubt of leadership gives way for hidden treasure to be found.  

The search for truth includes skepticism of the results.  Best to simply speak truthfully, and allow the truth to be humbly revealed.