"All right," said Susan, "I'm not stupid. You're saying humans need...fantasies to make life bearable."

NO. HUMANS NEED FANTASY TO BE HUMAN. TO BE THE PLACE WHERE THE FALLING ANGEL MEETS THE RISING APE.

"Tooth fairies? Hogfathers?"

YES. AS PRACTICE. YOU HAVE TO START OUT LEARNING TO BELIEVE THE LITTLE LIES.

"So we can believe the big ones?"

YES. JUSTICE. DUTY. MERCY. THAT SORT OF THING.

"They're not the same at all!"

REALLY? THEN TAKE THE UNIVERSE AND GRIND IT DOWN TO THE FINEST POWDER AND SIEVE IT THROUGH THE FINEST SIEVE AND THEN SHOW ME ONE ATOM OF JUSTICE, ONE MOLECULE OF MERCY. AND YET YOU ACT, LIKE THERE WAS SOME SORT OF RIGHTNESS IN THE UNIVERSE BY WHICH IT MAY BE JUDGED.

"Yes. But people have got to believe that or what's the point?"

MY POINT EXACTLY.

-Terry Pratchett The Hogfather