One of the oldest known riddles is the riddle (ainigma) of the Sphinx. In ancient Greek tradition the Sphinx devoured all those who failed to solve it, but she destroyed herself instead when Oedipus got the right answer.

In its best known form, it runs as follows:

What walks on four legs in the morning, two legs at noon, and three legs in the evening?

The answer is man: a person crawls on all fours when a baby, walks upright in the middle period of their life, and uses a walking stick when they are elderly.

What alternative solutions can you come up with?


Having been advised that the question as phrased above is too broad, and after imagining theatre-goers storming out of a production of Sophocles's Oedipus the King, loudly objecting that "The Sphinx's puzzle was completely unrealistic. It's obvious there's an infinite class of possible solutions, consisting of any quadruped entity that loses two legs and then gains back one", I am adding the following restriction:

please ensure that at least one interpretation of the word 'leg' is non-literal.

Further restriction

In response to votes to keep this question closed for still being "too broad" even after the addition of the first restriction, the original poster has decided to add a further restriction as follows.

Since this question is not considered reopenable as it stands, for being too broad, please make all answers refer either to the behaviour of vicunas (aspects of their behaviour not also displayed by other camelids) or to the developing relation between advertising, participatory commercial ('social') websites, right-wing libertarianism, the work culture of computer programmers, schizophrenia, bureaucracy, and the function of ritual respect-paying to 'good faith', but not both.


closed as too broad by Rand al'Thor, mmking, Spencerkatty, MisterEman22, Milo Brandt May 30 '15 at 16:32

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ If it's too broad and permits of a large number of good answers, as the person who voted to close clicked to say they think, then it's strange that a story passed down for more than 2000 years is premised upon the opposite view. Can you come up with a single good solution that isn't the known one? This is a difficult challenge and should stretch some of the many fine puzzling minds here. $\endgroup$ – h34 May 30 '15 at 14:36
  • 1
    $\begingroup$ A dog: when it was born it had four legs. Then it lost two legs from an exploding mine/bomb. A dog cannot walk on two legs, so it got a prosthetic leg. $\endgroup$ – mmking May 30 '15 at 14:51
  • $\begingroup$ @mmking - Please post it as an answer, and we'll see whether someone comes up with something better. It could also be a toy horse that someone cuts two legs off of and then sews one back on. Or a toy donkey. Or a toy mule. I'm three time as clever as Oedipus! :-) $\endgroup$ – h34 May 30 '15 at 14:54
  • $\begingroup$ I knew of an alternative wording: What walks on four legs in the morning, two legs at noon, three legs at dusk, and screams in abject terror now? :D $\endgroup$ – Alenanno Oct 8 '16 at 9:45

Napoleon in George Orwell's Animal Farm:

Four legs originally (naturally).
Then starts walking on two.
Then is propped up by the blood, sweat and tears (three things you see) of the proletariat beneath him.

Further explanation for those not familiar with Animal Farm:

Napoleon was the pig in charge of a revolt that led to the animals running their own farm. Like all pigs, he walked on four legs. In chapter 10, to the shock of the other animals, the pigs started walking on two legs (and carrying whips with Napoleon as a tyrannical dictator).

The primary message of the story is as a satire of Stalinist communism where the leaders of the revolution are as oppressive to the people as the aristocrats they replaced - hence the final three legs, which is a common phrase that means sacrifice and effort (see for example http://spectator.org/articles/56615/blood-sweat-and-tears).

  • $\begingroup$ Elegant! The third leg of the three in the third stage consists of three props! $\endgroup$ – h34 May 30 '15 at 16:13
  • $\begingroup$ Could you add just a bit of explanation for the benefit of people who haven't read this novel and who may not have a clue why Napoleon originally walked on four legs and so on? $\endgroup$ – h34 May 30 '15 at 16:25

Here's a slightly more literal answer than most...

Army buddies.

In the morning, they leave on a mission, walking on four legs.

In the afternoon, one of the buddies steps on a landmine, destroying one leg. The other buddy carries the injured one back to camp where there's a medic. Two legs.

In the evening, the medic has stitched up the injured buddy's stump, and hops, with the help of his buddy, to his cot - they are now walking on three legs between them.


A human, or bird, or anything else that satisfies the following:

  • evolved from four-legged ancestors (early primates/lizards in the case of humans/birds)
  • has two legs at the current stage of evolution
  • could conceivably evolve to have three legs in the future (heard of Frank Lentini?)
  • $\begingroup$ Nice. I hadn't heard of Frank Lentini, but this answer made me think of utopian socialist Charles Fourier, who thought humans would evolve to have long and useful tails. $\endgroup$ – h34 May 30 '15 at 16:19

A military dog:

  1. When it was born it had four legs.

  2. Then it lost two legs from an exploding mine/bomb.

  3. Its owner realized that a dog cannot walk on two legs and he was very stingy, so he got the dog one prosthetic leg. Now it has three legs.

  • $\begingroup$ Nice, but personally I think this is far too literal. $\endgroup$ – h34 May 30 '15 at 16:14

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