The Philosopher's Joke

A really intriguing short story about the lives of three couples in their forties, who are given the chance to go back through time, at the age of 20, with the knowledge of the future. What would a young person do, knowing that following his instinct would most probably lead to his wretchedness? How does one differentiate between reality and dream? How frightened is one, knowingly deciding to take the same steps in life the second time as he did the first time? (Goodreads)