“There lives more faith in honest doubt, Believe me, than in half the creeds.”
“I will listen to anyone's convictions, but pray keep your doubts to yourself.”
“There was a castle called Doubting Castle, the owner whereof was Giant Despair.”
“Faith keeps many doubts in her pay. If I could not doubt, I should not believe.”
“Suspicion amongst thoughts are like bats amongst birds, they never fly by twilight.”
“Philosophy when superficially studied, excites doubt, when thoroughly explored, it dispels it.”
“Neither in this world nor elsewhere is there any happiness in store for him who always doubts.”
“Doubt is the vestibule through which all must pass before they can enter into the temple of wisdom.”
“Everybody in the world thought we couldn't do it. But we did, dammit. [After winning the America's Cup]”
“Our doubts are traitors and make us lose the good we might win, by fearing to attempt.[Measure For Measure]”
“In all affairs it's a healthy thing now and then to hang a question mark on the things you have long taken for granted.”
“The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts.”
“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.”
“In contemplation, if a man begins with certainties he shall end in doubts; but if he be content to begin with doubts, he shall end in certainties.”
“Doubt, indulged and cherished, is in danger of becoming denial; but if honest, and bent on thorough investigation, it may soon lead to full establishment of the truth.”
“True wisdom is less presuming than folly. The wise man doubteth often, and changeth his mind; the fool is obstinate, and doubteth not; he knoweth all things but his own ignorance.”
“Suspicions that the mind, of itself, gathers, are but buzzes; but suspicions that are artificially nourished and put into men's heads by the tales and whisperings of others, have stings.”
“A person who doubts himself is like a man who would enlist in the ranks of his enemies and bear arms against himself. He makes his failure certain by himself being the first person to be convinced of it.”
“There is nothing more dreadful than the habit of doubt. Doubt separates people. It is a poison that disintegrates friendships and breaks up pleasant relations. It is a thorn that irritates and hurts; it is a sword that kills.”
“Doubt is to certainty as neurosis is to psychosis. The neurotic is in doubt and has fears about persons and things; the psychotic has convictions and makes claims about them. In short, the neurotic has problems, the psychotic has solutions.”
“Doubt, the essential preliminary of all improvement and discovery, must accompany the stages of man's onward progress. The faculty of doubting and questioning, without which those of comparison and judgment would be useless, is itself a divine prerogative of the reason.”
“There is no rule more invariable than that we are paid for our suspicions by finding what we suspect.”