I love this illustration on the nature of faith which originally appeared in the book Questions of Truth and was recently adapted in the PreachingToday newsletter:
"Philosopher Nicholas Beale and scientist John Polkinghorne use the following story to illustrate the nature of biblical faith:
"A philosopher, a scientist and a simple man—none of whom could swim—were trapped in a cove with sheer cliff faces. They split up, but the tide kept coming in. Rescuers lowered a rope with a safety harness. The philosopher said, 'Ah, this looks like a rope, but I might be mistaken—it could be wishful thinking or an illusion.' So he didn't attach himself, and he was drowned.
"The scientist said, 'Ah, this is an 11 mm polyester rope with a breaking strain of 2800 kg. It conforms to the MR 10-81 standard,' and then proceeded to give an exhaustive, and entirely correct, analysis of the rope's physical and chemical properties; but he didn't attach himself, and he was drowned.
"The simple man said, 'Ah, I'm not sure if it's a rope or a python tail, but it's my only chance, so I'm grabbing it and holding on with my whole life.' He was saved.
"Of course other things being equal, it is better to have an enlightened faith in God than an unenlightened faith, but mere intellectual understanding that does not lead to trust and action is not what God is after."