A ferryman is ready and waiting, with his small boat, on the tempestuous waters of a river. A philosopher, wishing to get to the other side, climbs aboard. There ensues the following dialogue:

Philosopher: Do you know anything of history, ferryman?
Ferryman: No!
Philosopher: Then you’ve wasted half your life! Have you studied mathematics?
Ferryman: No!
Philosopher: Then you’ve wasted more than half your life.

Hardly were these words out of the philosopher’s mouth when the wind capsized the boat, precipitating both ferryman and philosopher into the water. Whereupon,

Ferryman shouts: Can you swim?
Philosopher: No!
Ferryman: Then you’ve wasted your whole life.