Doubt is part of all religion. All the religious thinkers were doubters. - Isaac Bashevis
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. - Aesop
Doubt is the vestibule through which all must pass before they can enter into the temple of wisdom. - Charles Caleb Colton
You are a child of the Universe, no less than the moon and the stars; you have a right to be here. And whether or not it is clear to you, no doubt the Universe is unfolding as it should. - Max Ehrmann
Finish each day and be done with it. You have done what you could. Some blunders and absurdities no doubt crept in; forget them as soon as you can. Tomorrow is a new day; begin it well and serenely and with too high a spirit to be cumbered with your old nonsense. - Ralph Waldo Emerson
