The answer is a human being. This is the famous Riddle of the Sphinx from Greek mythology: “What walks on four legs in the morning, two legs at noon, and three legs in the evening?” The three stages represent a single human life. As babies, we crawl on hands and knees (four legs). As adults, we walk upright on two legs. In old age, we use a cane or walking stick as a third leg.
Why Morning, Noon, and Evening?
The riddle uses a single day as a metaphor for an entire lifetime. Morning represents childhood, noon represents the prime of adulthood, and evening represents old age. The creature is “weakest when it has the most” legs, meaning a crawling infant on all fours is more helpless than an adult standing on two. That extra detail appears in some versions of the riddle and adds a layer that makes the answer less obvious.
There’s an interesting wrinkle in how the metaphor actually plays out. When toddlers learn to walk, they don’t go straight from four legs to two. They typically use a hand for balance, either their own hand braced against furniture or an adult’s hand holding them steady. In a sense, children pass through a brief “three-legged” stage of their own before mastering two legs, making the human life cycle even more layered than the riddle suggests.
The Sphinx and the Story Behind the Riddle
In Greek mythology, the Sphinx was a creature with a lion’s body, a woman’s head, and large curving wings. She perched on a rock outside the city of Thebes and posed this riddle to every traveler trying to enter. Anyone who answered incorrectly was killed. The Sphinx terrorized the region so badly that King Laius of Thebes set out to consult the oracle at Delphi for help defeating her.
On the road to Thebes, a young man named Oedipus encountered the Sphinx and answered correctly: “Man.” The Sphinx, defeated, threw herself from the precipice. As a reward, Oedipus received the throne of Thebes and married the widowed queen, Jocasta. In one of mythology’s darkest twists, Jocasta turned out to be his own mother, a tragedy that had been prophesied before his birth.
The Sphinx’s Second Riddle
Some versions of the myth include a lesser-known second riddle. After Oedipus answered the first, the Sphinx posed another: “There are two sisters. One gives birth to the other, and in turn, the second gives birth to the first. Who are they?” Oedipus answered that the two sisters are day and night, each endlessly giving way to the other. This second riddle rarely appears in popular retellings, but it carries the same theme of cycles and the passage of time.
Greek Sphinx vs. Egyptian Sphinx
The Greek Sphinx that posed the riddle is quite different from the Great Sphinx of Giza. The Egyptian Sphinx is male, wingless, and was built as a monumental guardian statue. The Greek Sphinx was female, winged, and acted as a deadly riddler. As the image traveled from Egypt through Asia and into the Greek world, artists added wings to the lion’s body. By the later Greek period, the Sphinx was depicted as graceful and distinctly feminine, often wearing an elaborate tiered wig in the sculptural style of the era.
Why the Riddle Still Resonates
On the surface, this is a simple puzzle with a clever answer. But philosophers and psychologists have long argued that the riddle’s real power is what it says about self-knowledge. Oedipus answered “Man” and believed he had solved the mystery, yet he didn’t truly know himself. He didn’t know his real parents, his real origins, or the fate awaiting him. Some thinkers, particularly those influenced by Carl Jung, have pointed out that the Sphinx herself is a fitting symbol for the unconscious mind: part human, part animal, posing questions we can never fully resolve. Oedipus’s mistake wasn’t getting the riddle wrong. It was assuming that answering it meant he understood everything.
Sigmund Freud drew a similar parallel. He saw his own work on the unconscious as solving a kind of modern sphinx’s riddle, untangling the hidden drives behind human behavior. Later critics noted the irony: anyone who claims to have fully decoded the human mind has, in a sense, fallen into the same trap as Oedipus. The riddle’s answer is “a human being,” but the deeper question of what it means to be human doesn’t have a tidy solution.