“It is certain because it is impossible.”

“The Son of God was crucified: I am not ashamed--because it is shameful. The Son of God died: it is immediately credible--because it is silly. He was buried, and rose again: it is certain--because it is impossible. (Evans translation). z Tertullianus - De carne Christi”
Crucifixus est dei filius; non pudet, quia pudendum est. Et mortuus est dei filius; credibile prorsus est, quia ineptum est. Et sepultus resurrexit; certum est, quia impossibile.

“The life of a revolutionary would be quite impossible without a certain amount of "fatalism."”

“It is clear that thought is not free if the profession of certain opinions makes it impossible to earn a living.”

“We are too young to realize that certain things are impossible… So we will do them anyway.”

“Love between man and man is impossible because there must not be sexual intercourse and friendship between man and woman is impossible because there must be sexual intercourse.”

“It is almost impossible to state what one in fact believes, because it is almost impossible to hold a belief and to define it at the same time.”

“Credo quia impossibile.’ I believe it because it is impossible.”

“A classic is classic not because it conforms to certain structural rules, or fits certain definitions (of which its author had quite probably never heard). It is classic because of a certain eternal and irrepressible freshness.”

“Even if it meant that she had failed, she was glad. And if what she'd wanted had been impossible from the start, still there was a certain lonely comfort in the fact that she'd known it was impossible and had gone ahead and done it anyway.”