"I respect faith; but doubt is what gets you an education."

"To believe with certainty we must begin with doubting."

"I show you doubt; to prove that faith exists."

"If you would be a real seeker after truth; it is necessary that at least once in your life you doubt; as far as possible; all things. "

"Beliefs are what divide people. Doubt unites them."

"Doubt whom you will; but never yourself."

"The whole problem with the world is that fools and fanatics are always so certain of themselves; but wiser people so full of doubts. "

"A mind troubled by doubt cannot focus on the course to victory."

"There are two ways to slide easily through life; to believe everything or to doubt everything. Both ways save us from thinking. "