"If a man will begin with certainties, he shall end in doubts, but if he will be content to begin with doubts, he shall end in certainties." - Francis Bacon, The Advancement of Learning

"Certainty is the mother of quiet and repose, and uncertainty the cause of variance and contentions." - Edward Coke, The First Part of the Institutes of the Laws of England

"We can be absolutely certain only about things we do not understand." - Eric Hoffer, The True Believer

"It is the dull man who is always sure, and the sure man who is always dull." - Henry Louis Mencken, Prejudices

"Oh! let us never, never doubt
What nobody is sure about!"
- HILAIRE BELLOC, The Microbe

"Certainty generally is illusion, and repose is not the destiny of man." - OLIVER WENDELL HOLMES, JR., speech (1897)

"Certitude is not the test of certainty." - OLIVER WENDELL HOLMES, JR., Natural Law

"The only certainty is that nothing is certain." - PLINY THE ELDER, Natural History