The answer to the riddle "What has 4 legs in the morning, 2 in the afternoon, and 3 in the evening?" is a human being. In the morning of their life, they crawl on four legs as a baby, in the afternoon of their life they walk on two legs, and in the evening of their life, they may use a cane, which is like a third leg. This riddle comes from the myth of Oedipus, who solved the riddle of the Sphinx with this answer.