“The contrasts and contradictions that can permanently live peacefully side by side in a skull make all the systems of political optimists and pessimists illusory.”

“To the optimist, pessimists are neurotic; to the pessimist, optimists are deluded.”

“The optimist proclaims that we live in the best of all possible worlds; and the pessimist fears this is true.”

“We have found that our great philosophers and our great men of action are optimists. So, too, our most potent men of letters have been optimists in their books and in their lives. No pessimist ever won an audience commensurately wide with his genius, and many optimistic writers have been read and admired out of all measure to their talents, simply because they wrote of the sunlit side of life.”

“A pessimist is a man who has been compelled to live with an optimist.”

“Both optimists and pessimists contribute to society. The optimist invents the aeroplane, the pessimist the parachute.”

“Between the optimist and the pessimist, the difference is droll. The optimist sees the doughnut; the pessimist the hole! ”

“Don't ever become a pessimist, Ira; a pessimist is correct oftener than an optimist, but an optimist has more fun--and neither can stop the march of events.”

“Both optimists and pessimists contribute to our society. The optimist invents the airplane and the pessimist the parachute.”

“[…] You see, you are an optimist and live on hope. I am a pessimist and live on experience.”