Which is correct?:

Your question is very broad, and I doubt that it is answerable.

Your question is very broad, and I doubt if it is answerable.

Your question is very broad, and I doubt whether it is answerable.

  • 2
    I'd remove 'and' (or the comma) from all of them.
    – mcalex
    Feb 2, 2013 at 5:30
  • @mcalex. If you do that you create two clauses, which in writing would need to be separated by a period or a semi-colon. Feb 2, 2013 at 8:21
  • ok, so rip out the comma.
    – mcalex
    Feb 2, 2013 at 8:29
  • 1
    @mcalex: If we're going for the "slash and burn" approach, let's just go the whole hog with ...I doubt it is answerable. Nothing wring with that, imho. Feb 2, 2013 at 18:26

6 Answers 6


They all seem grammatical and reasonably idiomatic American English to me. It's a matter of style. I don't think any native speaker would have a problem understanding any of them, so I'd say that they're all "correct" in that sense.

"Correct" is a difficult word to define when it comes to English usage. If it's not ungrammatical, it may be grammatically correct, but it may not be something that a native speaker normally says, so then it wouldn't be idiomatically correct. Then, too, there's technically correct (the expected answers on internationally standardized English tests like the TOEFL and IELTS), and what your English teacher says is correct on his or her tests. I've seen myriad English tests in Taiwan and Japan, and most contain some multiple-choice questions that have no correct answers or many correct answers

I'd say and write #1, I wouldn't say or write #2, and if I were to use whether, I'd have to change "doubt" to "wonder". But, as I said above, it's strictly a matter of style in this case.

  • +1 for '"Correct" is a difficult word to define'. I suspect most native speakers could understand "Is you is or is you ain't my baby?". Feb 2, 2013 at 4:41
  • Most native speakers can also often understand various incorrect English spoken by foreigners, and word-for-word translations from other languages.
    – Kaz
    Feb 11, 2013 at 17:48

You've brought up an interesting problem. The word doubt, when used as a verb, generally expresses uncertainty, along with a lack of assurance or confidence, as in:

I doubt we will win the game.

Both doubt and don't know are ways to express uncertainty, but doubt connotes less confidence, while don't know suggests an inability to form a conclusion or hunch. In other words, if the weatherman says one of these two sentences:

I doubt it will rain tomorrow.
I don't know if it will rain tomorrow.

then neither is conclusive, but I'm more inclined to leave my umbrella home in the first case, but to at least bring it in my car in the second.

So, going back to your example sentences, I'm not sure I would use any of them. If I had real doubt that the question was answerable, I'd be more inclined to say:

Your question is very broad; I doubt it is answerable.

without putting any word between "doubt" and "it."

However, if I changed the verb to don't know, to express a higher level of uncertainty, I might use one of your options then:

Your question is very broad; I don't know if it's answerable.
Your question is very broad; I don't know whether it's answerable.

  • Doubt (at least to me) has a negative connotation in some uses. I have some foreign customers who react to some explanations by saying "We have some doubts". It helped the interaction to realize that this was more "there are some things we don't understand" than "we don't believe you". Feb 2, 2013 at 4:34
  • 2
    @Ross: Doubt is a noun there, not a verb; I'd interpret such remarks to have one of two meanings: either (a) "We have some misgivings," or (b) "We are skeptical about what you're saying." Although that would usually be construed as negative, there might be a few odd exceptions. For example, if a friend said, "I heard in a radio report that the Labor party was in trouble in the upcoming election," and I responded with, "Well, I have my doubts about that report," I could be expressing skepticism – but also a measure of optimism, depending on which side of the political spectrum I lean.
    – J.R.
    Feb 2, 2013 at 10:16
  • Is there any difference between "I doubt anyone slept that night," and "I doubt if anyone slept that night"?
    – apaderno
    Feb 2, 2013 at 15:28
  • @kiamlaluno: I doubt that there's any difference in meaning between those. (It seems like you could use "that" in place of "it" as well.) Cool Ngram on this.
    – J.R.
    Feb 2, 2013 at 19:17

All three are grammatical, but as a speaker of British English, I would normally say the second. However, doubt that occurs much more frequently in the Corpus of Contemporary American English, the British National Corpus and in citations in the Oxford English Dictionary than either doubt if or doubt whether, but we need to aim off to some extent for the occasions on which that will be a demonstrative pronoun rather than a subordinator.

The choice between if and whether in general can sometimes involve ambiguities, but these are normally resolved in speech by intonation. In writing, however, the choice can make a difference to the meaning. If someone sends us an invitation which includes the words ‘Please let us know if you’re coming’, we may think that we need to indicate our intention only if we plan to accept the invitation. If we don’t, we might conclude, there is no need to say anything. The writer, however, may have intended to us to reply in either case, and the use of whether rather than if would have avoided that difficulty.

  • good point about if.
    – user288
    Feb 2, 2013 at 17:53

This is an interesting question. The first point to note is there's no absolute rule of grammar involved here. OP's sentence is perfectly valid with that, if, whether, or indeed, nothing at all between the verb doubt and the statement which is doubted. The second point to note is that usage has changed...

enter image description here

From a quick glance, you might suppose that "if" is now the preferred conjunction, but focussing on American usage over the last few decades (usually a good indicator of where English is going)...

...it seems "no conjunction at all" is making a comeback from its C18 heyday. Which accords with my own perception, and – dare I say it – seems like the sensible choice. Why give yourself the problem of choosing between the other three possibilities, if you don't need to use any of them?

enter image description here

In case it's not obvious, the third point to make is that none of the variations convey any difference in meaning (not even a subtle nuance, so far as I'm concerned). Nor does formal/informal come into it.

Finally, here are links to three NGrams showing how doubt is falling into line with think and expect, in terms of not normally being followed by a superfluous "that".


My version would be something like this:

Your question is very broad, and I'm not sure if/whether it is answerable.

  • 1
    I don't see how this answers the question. All you've done is irrelevantly swapped am not sure for doubt, and tacitly ruled out "that". You give no reason for discarding one of OP's three suggestions, nor do you say anything about the relative merits of the remaining two. Feb 2, 2013 at 18:32
  • You are right @FumbleFingers but since I'm not a grammar expert, I didn't want to state something that might not be true. So I just gave my suggestion of how it could sound a lot better based on my experience dealing with native speakers for years. Feb 2, 2013 at 18:38
  • 2
    Arguably then it should have been posted as a comment. I wouldn't want to discourage people who aren't "grammar experts" from posting answers (I'm not one myself, to be honest), but it's difficult to see what future visitors will learn from this "answer", and (no slur on you) I don't understand why at least four people have chosen to upvote it. Feb 2, 2013 at 19:18
  • I see this website as a lighter version of english.stackexchange.com so that's why I posted as an answer and not as a commment. If the same question was asked there, I'd surely post it as a comment. Feb 2, 2013 at 20:00
  • 1
    It all depends what you mean by "lighter". Arguably in some cases it's "more okay" on ELU to mention, say, relatively uncommon usages that might be seen as pointlessly distracting detail on ELL. But I don't think the basic principles of "what constitutes an answer" should be more relaxed here. If a specific question is asked, any and all answers should address it - ideally, giving supporting references or reasoning. For example, do you actually have any reason for discarding OP's "that" from OP's list of alternatives? If so, I think you should give it. Feb 2, 2013 at 20:11

The word whether doesn't apply here because of a pattern which is consistent wh- words.

We cannot doubt a wh- proposition. These are all wrong:

  • {I doubt / I do not believe / I believe / I think / I'm sure } who will be there.
  • {I doubt / I do not believe / I believe / I think / I'm sure } what it is.
  • {I doubt / I do not believe / I believe / I think / I'm sure } when he will come.
  • {I doubt / I do not believe / I believe / I think / I'm sure } whether it will rain tomorrow.

These are right:

  • {I don't know / Tell me / I wonder / I'm not sure} who will be there.
  • {I don't know / Tell me / I wonder / I'm not sure} what it is.
  • {I don't know / Tell me / I wonder / I'm not sure} when he will come.
  • {I don't know / Tell me / I wonder / I'm not sure} whether it will rain tomorrow.

In a nutshell the reason is that, Wh- words are embedded questions. For example, by itself, who will be there is a question: Who will be there?. And you cannot doubt a question! You can only doubt a statement (such as the answer to a question). A question is itself an expression of doubt.

Also, note how the presence or absence of the word not does not make a difference in I do not believe. However, the not makes a difference in: I'm not sure. This is a semantic matter rather than purely syntactic: it has to do with meaning rather than grammar.

Now about if. The word if, in this situation, is a substitute for whether that many modern English speakers use. It can also substitute for that, but these two usages are not on the same level. I wonder if it will rain (if substituting for whether) is broadly acceptable and can be used in formal writing, but I doubt if it is true (if substituting for that) is still very colloquial.

The likely reason why if instead of that is less acceptable is that if instead of whether serves a useful purpose: it provides economy of expression. if is only one syllable and phonetically easier than whether. Not to mention that it is two letters instead of seven, in writing. But the word that can be economized by a complete omission: if that is troublesome to say or write, you can usually just drop it entirely! So there is no point in replacing it with if. Quite simply, I doubt it is true.

  • 1
    I dispute the claim that to doubt whether something is true is somehow grammatically "wrong". It may not be so common today, but for over 40 years in C19 it was actually the most popular choice. No new rules of grammar have been introduced since then which would make this an invalid construction. Feb 2, 2013 at 19:11
  • Try this search instead. It is less specific.
    – Kaz
    Feb 2, 2013 at 20:36
  • 1
    But by the very fact of being "less specific", that search term erroneously suggests that to doubt that was actually the more common usage during that period! An error caused purely by the fact that the "looser" search pulls in more "false positives" - I just checked the first two pages of results on your link; less than half of them actually involve the word "doubt" being used as a verb, which is our context here. Whereas virtually every single instance in my search will be a genuinely relevant verb usage. Feb 2, 2013 at 22:04

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