"You never know how much you really believe anything until its truth or falsehood becomes a matter of life and death to you. It is easy to say you belive a rope to be stong and sound as long as you are merely using it to cord a box. But suppose you had to hang by that rope over a precipice [face of a cliff]. Wouldn't you then first discover how much you really trusted it?" C.S. Lewis, A Grief Observed