“One must know how to doubt.”
“The goals you will attain are the ones you know whitout a doubt that you must reach in order to fulfill your own best possibilities”
“Doubts are the innermost corner of our souls. One must not talk about his doubts, whatever they may be.”
“One must ask for death to know how good it is to live”
“A doubtful friend is worse than a certain enemy. Let a man be one thing or the other, and we then know how to meet him.”
“We must doubt the certainty of everything which passes through the senses, but how much more ought we to doubt things contrary to the senses, such as the existence of God and the soul.”