Hacker News Reader

> 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.

View on HN

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.

While it pains me to admit: They're actually right, and I was wrong above.

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

Reply on news.ycombinator.com