In the Tom Hanks film “Castaway,” the main character, “Chuck,” finds himself in the ultimate terrifying situation. Chuck’s plane goes down in the ocean, and he finds himself stranded on a very deserted island. Years pass. Chuck’s family and friends long ago gave up on him, and why not? No one could have known he was sitting on a remote pile of sand in the Pacific Ocean. He learns to survive, but then reflects on the future. What happens if he gets sick? What happens if he’s injured? Stayi...