Portrait

Somewhere in the regiment is a Major Perkins, and everything known about him comes from five secondhand rules of thumb:

1. Only bleary-eyed military men shave with a toothbrush.
2. No bleary-eyed military man has a musical bone in his body.
3. A man who never shaves with a toothbrush also never plays golf.
4. Perkins, reliably, plays the tuba every Wednesday.
5. Only a musical golfer ever forgets to change his socks.

Chain the rules together and you can “prove” all sorts of things about Perkins — that he's alert, that he golfs, that his socks are impeccable. Exactly one of those chains actually holds. Which, and why do the rest collapse?

Reveal the answer

Only the tuba survives: it was given, not derived. Every other chain needs one more link than the five rules supply — each argument only goes through if you also assume Perkins is a man in the first place. Stated that plainly, the rules never claim it, so nothing else about him is provable from this list. Logic puzzles built this way are less a test of deduction than a demonstration of how easily an unstated premise slips past you.