Not to be absolutely certain is, I think, one of the essential things in rationality.Bertrand Russell
Refusal to believe until proof is given is a rational position; denial of all outside of our own limited experience is absurd.Annie Besant
No rational argument will have a rational effect on a man who does not want to adopt a rational attitude.Karl Popper
Beware of being too rational. In the country of the insane, the integrated man doesn't become king. He gets lynched.Aldous Huxley