"If it quacks like a duck, then it must be a duck. Now suppose you are aware that there is only one duck in the world, and you have just found an animal that quacks. Then, by golly, you have found the duck!"
I quoted that from a very nice book called A Transition to Abstract Mathematics by Randall B. Maddox. I'm only into the second chapter, and this book already has the potential to be one of my favorites.
Logically equivalent statements: If it quacks like a duck, then it must be a duck = If it is not a duck, then it doesn't quack like a duck.
And, of course, this is assuming that a duck is defined as an animal that has the property of quacking. So far I have not met any counter examples to this... unless you consider me after I am sufficiently intoxicated, as my duck impressions then can probably make a real duck question the meaning of its own existence... in which case we'd have a very depressed duck.
My insights: Ducks, despite their survival benefits to the plant and animal kingdom as a whole, have been raised by nature for the sole purpose of quacking and being quacked at.  |
