From a math textbook I was reading recently -- the legendary philosopher in action:
[A] proof containing a single error in reasoning cannot be considered "nearly correct"; we can derive any conclusion from a single false statement. Bertrand Russell (1872-1970) once stated this in a public lecture and was challenged to start with the assumption that 1=2 and prove that he was God. He replied, "Consider the set {Russell, God}. If 1=2, then the elements of the set are one element, and therefore Russell=God."
That may be apocryphal, but if true, it's a hell of a line to come up with off the top of your head.
Update 7/5: In comments, Michael Koplow directs us to a demonstration of the same principle in Zero: The Biography of a Dangerous Idea. The author, Charles Seife, intentionally divides by zero to show that it allows him to prove that Winston Churchill is a carrot. Here's the Amazon Search Inside the Book link so you can read it for yourself.
Very cool indeed. For a similar but slightly longer exercise, see appendix A of Charles Seife's _Zero: The Biography of a Dangerous Idea_. There he proves that Winston Churchill was a carrot by allowing division by zero.
Posted by: Michael Koplow | July 05, 2005 at 09:58 PM
That is a big "if".
Since he was in a "public lecture", that means he was already famous and thus, this wasn't his first public lecture.
Odds are, someone, in public or private, came up with it before. I read that Richard Fyenman practicised giving quick retorts. I don't know how he practicised but I couldn't finish the article.
Posted by: Terry | July 05, 2005 at 09:59 PM