It has become a certainty now that if you will only advertise sufficiently you may make a fortune by selling anything.
Anthony Trollope
Doubt is not a pleasant condition, but certainty is absurd.
Voltaire
Moral certainty can deafen people to any truth other than their own.
Geraldine Brooks
Our need for certainty in an endeavor as uncertain as raising children makes explicit 'how-to-parent' strategies both seductive and dangerous.
Brene Brown
I don't have Gandalf the White's certainty about everything.
Ian Mckellen
Science has proof without any certainty. Creationists have certainty without any proof.
Ashley Montagu