There are some who laugh off paradoxes and scorn the idea that serious harm can come from them. Well, let me warn you all: Paradoxes can be lethal. Just ask Philetas of Cos, who worried about the Liar Paradox so much that he wasted away until he had to put lead weights in his shoes to stop himself from blowing over in the wind. It killed him in the end. Allow me to suggest some guidelines for practicing safe paradoxing.

Paradox don’ts:
  • Don’t use paradoxes to confuse a computer that is also controlling the life support systems you rely on.
  • Don’t use a paradox (specifically a time paradox) to turn an interesting sci-fi into a dull and boring one.
  • Don’t cause your friends to waste away by forcing them to contemplate paradoxes (unless you own an otherwise struggling shoes-with-lead-soles factory).
  • If you travel back in time, don’t ever kill an ancestor before they’ve done the necessary with another ancestor of the opposite sex. Even then, be careful.
  • If you live in a fragile universe, try to move to one that doesn’t just cease to exist whenever a major paradox occurs.
  • Don’t confuse a simply difficult problem with a real paradox, or you’ll never work out which of the lying or truthful monsters is guarding the gate to safety.
  • Don’t ever give a tortoise a head start, no matter how small, in a race.

Paradox do’s:
  • Use a paradox to disprove interesting mathematical ideas – like “the square root of 2 is rational”, or more interestingly the halting dog problem. Some of these could win you fame.
  • Use a paradox to illustrate inconsistency in an opponents argument. Socrates is remembered for this. Actually now that I come to think about it, he also irritated everyone until he was executed for it. Perhaps this should be a “don’t”.
  • Use paradoxes to explain why you couldn’t possibly do your Maths homework.
  • Do use condensed paradoxes (oxymorons) to make satirical references to a certain office software package. This will win you friends. In fact, always be on the look out for oxymorons.