Richard Dawkins on Faith
The Selfish Gene (New edition, New York: Oxford University Press, 1989), p. 198.
Faith cannot move mountains (though generations of children are solemnly told the contrary and believe it). But it is capable of driving people to such dangerous folly that faith seems to me to qualify as a kind of mental illness. It leads people to believe in whatever it is so strongly that in extreme cases they are prepared to kill and to die for it without the need for further justification.