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The following is a "puzzler" from CarTalk. I find it relevant to complex systems and unintended consequences because it illustrates two principles that are important when thinking about complex systems.

  1. It's important to understand and make use of the environment within which something is operating — and the other agents within that environment.
  2. When a mechanism is created and installed in the world, it may be used in unexpected ways.

Here's the statement of the puzzler.

Mr. Black, Mr. Brown and Mr. White so detest each other that they decide to resolve their differences with pistols. It's kind of like a three-way duel. And unlike the gunfights of the old West, where the participants would simultaneously draw their guns and shoot at each other, these three gentlemen have come up with a rather more civilized approach.

Mr. White is the worst shot of the three and hits his target one time out of three. Mr. Brown is twice as good and hits his target two times out of three. Mr. Black is deadly. He never misses. Whomever he shoots at is a goner.

To even the odds a bit, Mr. White is given first shot. Mr. Brown is next, if he's still alive. He's followed by Mr. Black, if he's still alive.

They will continue shooting like this, in this order, until two of them are dead.

As the first shooter but the worst shot, at whom should Mr. White aim to maximize his chances of surviving?

Here's the answer.

Mr. White should aim at no one. He should miss. By doing so, he ensures that one of the better shooters, Mr. Black or Mr. Brown, will be eliminated and that he, Mr. White, will get first shot at the remaining gunman.

If Mr. White shoots wildly, then Mr. Brown and Mr. Black have to go at each other rather than after Mr. White since he is so much less of a threat. So after Mr. White misses, Mr. Brown whose shot it is now will obviously take aim at Mr. Black. If he misses then Mr. Black will return fire and kill Mr. Brown. But no matter what, it's now Mr. White's shot again. So by shooting into the air he guarantees himself a second shot. He's still a lousy shot, one in three. But at least he gets to shoot first at the one and only opponent still standing. If, on the other hand, Mr. White shoots and kills one of the other gunmen, the remaining gunman would have first shot at him.