Recently, while driving between the Eastern Fortress and the Geekplex, I wound up behind a giant, sticker-festooned SUV. This being Tampa, I didn’t consider this terribly uncommon. There were the usual “NObama” and “My kid’s an honor student” adornments, but one in particular stuck in my head.
The back window was dominated by a drawing of a very angry-looking Pit Bull Terrier, and surrounding it were these words: “If it ain’t a Pit, it ain’t shit!”
What we have here, basically, is the statement: “If not A, then not B.”
The rules of logic are vicious and unforgiving. If the statement evaluates as true – and we must assume it does because it’s being stated in an axiomatic manner – then it’s a logical necessity that the contrapositive must also be true. Flip A and B, take out the nots, and we find the contrapositive to be: “If B, then A.”
Plug back in our terms, and the statement becomes “If it’s shit, it’s a Pit”.
Moral of the story: double negatives are bad. And, quite often, they’re unintentionally funny.