The unique and supreme voluptuousness of love lies in the certainty of committing evil. And men and women know from birth that in evil is found all sensual delight.

When I talked to my medical friends about the strange silence on this subject in American medical magazines and textbooks I gained the impression that here was a subject tainted with Socialism or with feminine sentimentality for the poor.

I haven't been faithful to my wife. Our marriage has been tainted with my infidelities. I was irresponsible.

I tore myself away from the safe comfort of certainties through my love for truth - and truth rewarded me.

Probability is expectation founded upon partial knowledge. A perfect acquaintance with all the circumstances affecting the occurrence of an event would change expectation into certainty and leave nether room nor demand for a theory of probabilities.

I feel sometimes as the renaissance man must have felt in finding new riches at every point and in the certainty that unexplored areas of knowledge and experience await at every turn.

I found it peculiar that those who wanted to take military action could - with 100 per cent certainty - know that the weapons existed and turn out to have zero knowledge of where they were.

Knowledge is an unending adventure at the edge of uncertainty.

Dogmatism and skepticism are both in a sense absolute philosophies one is certain of knowing the other of not knowing. What philosophy should dissipate is certainty whether of knowledge or ignorance.

Jealousy lives upon doubts. It becomes madness or ceases entirely as soon as we pass from doubt to certainty.