At the GOP debate I didn't see last night, Mike Huckabee said this:
“The Air Force has a saying that says if you’re not catching flak, you’re not over the target,” he said. “I’m catching the flak; I must be over the target.”
Matt Yglesias has a chuckle and responds:
This is basically a form of affirming the consequent. If you're over the target, you'll catch flak and Huckabee is catching flak "therefore" he must be over the target.
Except, no it isn't. Affirming the consequent is reasoning if p then q, q, therefore p, which is a corrupted form of modus ponens: if p then q, p, therefore q. That's not what's going on here. Let's say p = x is not catching flack, and q = x is not over the target. Huckabee is denying the antecedent: if p then q, not p, therefore not q; this is a corrupted form of modus tollens: if p then q, not q, therefore not p.
Incidentally, the Air Force is wrong. Not taking flak doesn't imply not being over the target: for example, you could be over the target when the flak cannon malfunctions, in which case you'd be not taking flak, but over the target. Huckabee, it turns out, is accidentally right because of a true modus ponens argument: if you're catching flack, you're over the target; he's catching flack, therefore....
The moral: If you want to make fun of hillbilly logic, it's probably a good idea to doublecheck your own work. Just saying.
Links:
[1] http://matthewyglesias.theatlantic.com/archives/2008/01/is_mims_affirming_the_conseque.php
[2] http://en.wikipedia.org/wiki/Affirming_the_consequent
[3] http://en.wikipedia.org/wiki/Denying_the_antecedent