“The most irresistible compulsion for me is that of doubt. I have doubts about all, including my own doubtfulness. I believe little, and that not fully. Scepticism is for me not a "fine art" but an integral part of my existence.”

“My principal sin is doubt. I doubt everything, and am in doubt most of the time.”

“I have studied at Barcelona, at Salamanca, at Alcala, at Paris; what have I learned? The language of doubt; but in me there was no harbor for doubt. Jesus came, and my trust in God has grown by the doubts of men.”

“I don't believe anyone ever suspects how completely unsure I am of my work and myself and what tortures of self-doubting the doubt of others has always given me.”

“People have doubted me and criticized me my whole life, and that's why I'm the way I am.”

“Sometimes I doubt and sometimes I believe. And I like not making myself believe when I am doubting, and not making myself doubt when I am believing. Surely neither God nor Accident need my consistency.”

“They're all crazy. They're all crazy except you and me. Sometimes I have me doubts about you.”

“I have no patience for anybody that doubts me, none at all.”

“My old skill at self-delusion overrode my doubts as I told myself that Dexter probably believed in me. I could believe anything then. I still can as long as it is improbable.”

“I had never doubted my own abilities, but I was quite prepared to believe that "the world" would decline to recognize them.”