Comment by tr352
9 years ago
> A -> B does not imply !B -> !A
A -> B does imply !B -> !A. The error in reasoning here seems to be that attitude towards a website is assumed to be a binary "like/not like" variable, while in reality one can also neither like nor dislike something.
No it doesn't. Just because you tell me you don't like to get shot doesn't mean you are ok with being stabbed.
Yes it does. In fact, in classical logic, A->B is equivalent to !B->!A. See https://en.m.wikipedia.org/wiki/Contraposition
Exactly.
A consequence of this being true is the Raven Paradox [1], seemingly the OP has solved the classic riddle in a HN thread.
[1] https://en.wikipedia.org/wiki/Raven_paradox
While it pains me to admit: They're actually right, and I was wrong above.