Perhaps the most famous riddle of all time contains a metaphor of life stages. In ancient Greece, a monster called the Sphinx accosted travelers near the city of Thebes and asked them, “What is the...

Perhaps the most famous riddle of all time contains a metaphor of life stages. In ancient Greece, a monster called the Sphinx accosted travelers near the city of Thebes and asked them, “What is the animal that walks on four legs in the morning, two legs at noon, and three legs in the evening?” Anyone who gave a wrong answer was devoured! Many tried to answer—all unsuccessfully—until a stranger named Oedipus stepped forward with the solution: “Man. He crawls on his hands and knees as a child, walks on two legs as an adult, and uses a cane in old age.”