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I'm well aware of the logical contrapositive in the form: if A implies B, then Not B implies Not A. I've used this fact, unprompted, in a variety of contexts.
by Enginerrrd 6y ago
I'm well aware of the logical contrapositive in the form: if A implies B, then Not B implies Not A. I've used this fact, unprompted, in a variety of contexts.
However, there's something about the way this guy asked the question that makes me unsure whether I would have correctly answered it on the spot. It's somehow detached from both application, and the logic that underlies it.
If the question had been asked as: "Is there any relationship between Not A and Not B" I would have instantly gotten the correct answer.
...But the way he asked it, it comes across as a question about whether Not A implies Not B which of course does not follow the given. I realize none of those words are in actually in there, yet the phrasing of the question somehow leads my brain into filling in the gaps in that way. My suspicion is that this is actually a common thought pattern and perhaps those being interviewed may have fallen into a similar trap.
- sampo 6y ago> What can we say about `not A' and `not B'? Haha, yes. I interpreted the `and` in that sentence as the logical connective, and (A → B) says nothing about (¬A ∧ ¬B). But he meant `and` in the human language sense.
- mrfredward 6y agoThe author compares it to asking about 2+2, but I think it's more closely analogous to asking "What can we say about 4 and 2+2?" Given the ambiguous wording, I wouldn't expect anyone to answer confidently, and lost of intelligent people would answer eight rather than "they're equal."
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- deleted 6y ago[deleted]
- notJim 6y agoI agree this question is phrased very strangely in a way I find hard to parse. Perhaps this is a common way of speaking in academia, but "what can we say about…" was not a phrase I immediately understood. I was also unsure if he meant `not A AND not B` or, casually, `not A` and also `not B`. If it was phrased more precisely, I think I would have been able to answer better. This whole thing reminds me of old-style, bad tech interviews where the interviewer is really selecting for someone similar to themselves, i.e., someone who understands a particular obscure phrasing of a problem, and immediately knows the correct answer. However, he does point out that he tried explaining things, and different phrasing, so maybe there really is something here.