“Believe in angels? Then believe in vampires. Believe in me. There are worse things on earth.”

Source: The Hour of the Star

Douglas J. Rowe: The Associated Press (June 14, 2004) "Film bad guy Walken: 'Slow and steady is a very good thing for me'", The Grand Rapids Press, p. D5.

"Child of the Night" in 100 Vicious Little Vampire Stories (1995) edited by Robert Weinberg, Stefan Dziemianowicz, and Martin H. Greenberg

Letter to William Eustis http://books.google.com/books?id=S088AAAAIAAJ&pg=PA319 (22 June 1809), published in Writings of John Quincy, Adams (1914), The Macmillan company.
Variant: All men profess honesty as long as they can. To believe all men honest would be folly. To believe none so is something worse.

Will and Mary in Ch. 33 : Marzipan
His Dark Materials, The Amber Spyglass (2000)
Context: They lay back, well fed and comfortable in the flower-scented night, and listened to Mary tell her story.
She began just before she first met Lyra, telling them about the work she was doing at the Dark Matter Research group, and the funding crisis. How much time she’d had to spend asking for money, and how little time there’d been left for research!
But Lyra’s coming had changed everything, and so quickly: within a matter of days she’d left her world altogether.
"I did as you told me," she said. "I made a program — that’s a set of instructions — to let the Shadows talk to me through the computer. They told me what to do. They said they were angels, and — well…"
"If you were a scientist," said Will, "I don’t suppose that was a good thing for them to say. You might not have believed in angels."
"Ah, but I knew about them. I used to be a nun, you see. I thought physics could be done to the glory of God, till I saw there wasn’t any God at all and that physics was more interesting anyway. The Christian religion is a very powerful and convincing mistake, that’s all."

Source: The Dresden Files, Grave Peril (2001), Chapter 24
Context: Michael Carpenter: I still can’t believe, that you came to the Vampires’ Masquerade Ball dressed as a vampire.
Harry Dresden: Not only that, but a cheesy vampire.

Pinter on Pinter in The Observer (1980)

Source: Death by Black Hole - And Other Cosmic Quandaries