Curiosity is one of the permanent and certain characteristics of a vigorous intellect.
—Samuel Johnson
If an elderly but distinguished scientist says that something is possible, he is almost certainly right; but if he says that it is impossible, he is very probably wrong.
—Arthur C. Clarke
Human beings are perhaps never more frightening than when they are convinced beyond doubt that they are right.
—Laurens Van der Post
Too bad the only people who know how to run the country are busy driving cabs and cutting hair.
—George Burns
An atheist has to know a lot more than I know. An atheist is someone who knows there is no god. By some definitions atheism is very stupid.
—Carl Sagan
Life is always uncertain. We cannot let the fear of what might happen stop us living as we choose.
—Susanna Kearsley in The Rose Garden
Not to be absolutely certain is, I think, one of the essential things in rationality.
—Bertrand Russell
I am certain there is too much certainty in the world.
—Michael Crichton
Everybody knows how to raise children, except the people who have them.
—P.J. O'Rourke
Aristotle maintained that women have fewer teeth than men; although he was twice married, it never occurred to him to verify this statement by examining his wives' mouths.
—Bertrand Russell
There are as many opinions as there are experts.
—Franklin D. Roosevelt
If the world should blow itself up, the last audible voice would be that of an expert saying it can't be done.
—Peter Ustinov
But in this world nothing can be said to be certain, except death and taxes.
—Benjamin Franklin
A fellow who is always declaring he's no fool usually has his suspicions.
—Wilson Mizner
All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident.
—Arthur Schopenhauer