We’re descended from the indignant, passionate tellers of half truths who in order to convince others, simultaneously convinved themselves. Over generations success had winnowed us out, and with success came our defect, carved deep in the genes like ruts in a cart track—when it didn’t suit us we couldn’t agree on what was in front of us. Believing is seeing. That’s why there are divorces, border disputes and wars, and why this statue of the Virgin Mary weeps blood and that one of Ganesh drinks milk. And that was why metaphysics and scince were such courageous enterprises, such startling inventions, bigger than the wheel, bigger than agriculture, human artifacts set right against the grain of human nature.
-- Ian McEwan, Enduring Love (1998, p. 181)