## "If not, why?" vs. "If not, why not?"

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1

1. If Oscar Wilde was right, or partially right, what are the reasons? If not, why not?

2. If Oscar Wilde was right, or partially right, what are the reasons? If not, why?

Is "not" needed after "why" in the latter question? What's the difference between the questions, if any?

I think both are same. 1st one is If he was not right, why not is he right? and the 2nd one is If he was not right, why is it so? (The italicized parts are not said explicitly) – Mistu4u – 2013-01-26T08:31:55.850

1

Yes, you do need the not at the end.

You've got a sort of a parallel construction going on, with some paraphrasing to make it less duplicative. You could rephrase the entire thing thus:

Was Oscar Wilde right (or partially right)? If so, why? If not, why not?

When you are asking about a situation with an explicit negation such as not in it, your question about it needs to match it:

You don't think he was right? Why not?

He didn't like the cake? Why not?

In this case, your second piece of the question is a shortened form of "If [he was] not [right]" and therefore you must ask "why not?" to properly match it.

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Answers above are correct: both variants can be used, but the meaning is slightly different.

To grasp what's going on, remember that in English, complete Subject-Verb structures are required. They are often skipped in a colloquial speech, but they are always needed to completely "unroll" the full sentence:

If he was right, why {was he right}? If {he was} not {right}, why {was not he right}?
If he was right, why {was he right}? If {he was} not {right}, why not {was he right}?

"If not, why?" may also imply a continuation:

If he was right, why {was he right}? If not, why {do you think so}?

Something like this (sorry for my poor drawing):

    ↓────────────────────┐     ┌────┐
↓─────────────┐      │     │    ↓
If he was right, why? If not, why {do you think so}?


Or, simply:

    ↓────────────────────┐ ┌───┐
↓─────────────┐      │ ↓   │
If he was right, why? If not, why?


OTOH, "If not, why not?" is pointing directly to an original phrase:

    ↓───────────────────────────────┐
↓─────────────┐            ┌──↓ │
If he was right, why? If not, why not?


3

"Not" isn't needed after the why in the example question.

The reason for this is that you have already given a reason for the why - "If not, why" the "If not" part being the question opener, you simply do not need to add the not again.

The "If not" part adds the meaning of the question as, "If the answer to the previous question is No, why did you say No?".

"If not, why not?", could be used, but it is very uncommon to see it being used.

3I see that you're from the UK. "If not, why not?" is actually rather common in (at least parts of) the US; I'm sure I heard my mother say it, and she was a schoolteacher (though many years ago). "If not, why?" would be much less usual here. So I suspect the difference may be regional. (They do mean the same to me, though.) – barbara beeton – 2013-01-25T19:59:55.607

2I'm more familiar with British English than American English, still I'd go with the first option (If not, why not?), the reason for this being that the full question would be "if not, why wasn't he right?". I understand the meaning would be the same, but the second question sounds incomplete to me. – Paola – 2013-01-26T00:01:04.260

1I've got to agree with @Paola: "if not, why?" doesn't work. – Hellion – 2013-01-26T05:09:08.740

@barbarabeeton It has nothing to do with British English. I am from the US, and I rarely see "If not, why not?". I think this redundant usage is colloquial, and "If not, why?" is more formal. – ctype.h – 2013-01-26T06:10:38.207

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Repetition is metaphorically a sin in English Language. We occasionally are forced to use the pronouns or eliminate the unneeded phrase which is repeated. Here, we are repeating the word "not", but the good news is that we can use pronouns or eliminate as well.

To avoid repetition, here are two sentences that seem fine:

• If not, why so?

• If not, why?

As an addendum, I would provide another of eliminating extra words.

In the following sentence in passive voice, we may eliminate the phrase "by someone", but it is not necessary.

The wires were cut by someone.

repetition is not a sin. What gives you that idea? – Matt Ellen – 2013-01-26T10:15:26.583

@MattEllen Hyperbole. – Parth Kohli – 2013-01-26T10:21:57.627

1But there is no reason to remove the duplication. "If not, why not?" is idiomatic English. Much like "to be or not to be", "so-so", "good, good", etc., etc. – Matt Ellen – 2013-01-26T12:57:14.700

1"If not, why so?" sounds like a contradiction. – Hellion – 2013-01-26T16:26:47.780