Un-Priori

My physical therapist told me I'd need to ice my knee for a few days. I asked if it would need more than one icing per day. She laughed bitterly. "More than once per day? I should hope so!" It was plainly ridiculous to imagine any therapeutic effect at all from a mere single application. I was directed to ice it three times.

She was making an a priori argument in a situation that couldn't support it. If 5 icings were required, or 20 or 150, one might just as easily ridicule the notion of three daily icings.

Years earlier, a friend invited me along to a Wayne Shorter concert. He had an extra ticket. As we filed into our seats for the performance, I asked how much I owed him. "$100" he said. My mouth fell agape. "A hundred dollars? Really?" He looked at me like I was a boob. "It's Wayne Shorter! A legend! Would you really argue that Wayne Shorter isn't worth $100?"

"Why not $13,000?" I replied. Is Wayne Shorter not worth $13,000? Honestly, a mere thirteen grand sounds like a steal to hear one of the all-time greats!

Ice is therapeutic and Wayne Shorter is great. In these cases, they're indisputable assertions. But neither assertion, on its own, supports a particular numerical conclusion.

I hereby coin the term “Un-Priori Argument” for arguments where the conclusion is presumed to ride along on the self-evidence of an undisputed premise. It’s a form of non sequitur (where the conclusion doesn’t follow from the premise), in which the conclusion tries to borrow authority from the premise.