“"… If ever I murdered somebody," he added quite simply, "I dare say it might be an Optimist."
"Why?" cried Merton amused. "Do you think people dislike cheerfulness?"
"People like frequent laughter," answered Father Brown, "but I don't think they like a permanent smile. Cheerfulness without humour is a very trying thing."”

Source: Is Everyone Hanging Out Without Me?

1990s, Ed Gordon interview (1994)

From interview with Rajeev Masand

The Dagger with Wings (1926)

Source: Eisner/Miller (2005), p. 95

Source: Down and out in Paris and London (1933), Ch. 30
Context: He was an embittered atheist (the sort of atheist who does not so much disbelieve in God as personally dislike Him), and took a sort of pleasure in thinking that human affairs would never improve. Sometimes, he said, when sleeping on the Embankment, it had consoled him to look up at Mars or Jupiter and think that there were probably Embankment sleepers there. He had a curious theory about this. Life on earth, he said, is harsh because the planet is poor in the necessities of existence. Mars, with its cold climate and scanty water, must be far poorer, and life correspondingly harsher. Whereas on earth you are merely imprisoned for stealing sixpence, on Mars you are probably boiled alive. This thought cheered Bozo, I do not know why. He was a very exceptional man.

Posthumous attributions, Tupac: Resurrection (2003)