Heron Suit

[Dave Britten]

This is from Professor Stewart's Cabinet of Mathematical Curiosities, a rather good book so far. Should make for good beach/camping reading

The logic on this one particular puzzle isn't adding up for me, though.

Quote:No cat that wears a heron suit is unsociable.
No cat without a tail will play with a gorilla.
Cats with whiskers always wear heron suits.
No sociable cat has blunt claws.
No cats have tails unless they have whiskers.
Therefore:
No cat with blunt claws will play with a gorilla.
Is the deduction logically correct?

I came up with yes, it is. But then I checked the answer in the back of the book. (Spoilers below.)

Quote:The deduction is incorrect. Consider a cat with blunt claws that plays with a gorilla, does not wear a heron suit, has a tail, has no whiskers, and is unsociable. The first five statements are all true, but the sixth is not.

Wait, huh?

Quote:No cats have tails unless they have whiskers.

Quote:...has a tail, has no whiskers...

Am I parsing that wrong, or do those two qualities contradict rule five? To me, that rule reads "tail -> whiskers".