“The the question whether I am a pessimist or an optimist, I answer that my knowledge is pessimistic, but my willing and hope are optimistic.”
“I am neither an optimist nor pessimist, but a possibilist.”
“I am by nature an optimist and by intellectual conviction a pessimist.”
“I guess I'm a hopeful optimist, because to be a pessimist is to be suicidal.”
“The difference between an optimist and a pessimist? An optimist laughs to forget but a pessimist forgets to laugh.”
“Both optimists and pessimists contribute to society. The optimist invents the aeroplane, the pessimist the parachute.”