All cats have three tails

So if you take one cat with one tail and add the no cat with two tails to it you end up with one cat who must have three tails.

Sir, I think you are abusing the english language.

Sir, I have had the honor of receiving a communication from Lady Worplesdon on the telephone. Madam directs me to convey her wish that you cease this infantile piffle immediately. The expression is hers, sir.

But Jeeves, dash it, the thing is some kind of logic thingy. Very improving for the mind, I dare say, and the Wooster fiancee spent last evening in loving conference with self explaining it to me until I got it. Dashed domestic, what? Well-nigh connubial. How the blasted Aunt Agatha, blast her, can kick at these scenes of settled bliss is more than I can explain.

Reminds me of DeMorgan’s paradox where in a few lines of algebra clearly prove that 1=0. And in some contexts, this is tremendously useful.