So sometimes I say,

[conuly]

or hear other people say, "I don't know that something or other" and other times I say or hear "I don't know if something or other". I vaguely feel as though there is some sort of distinction here, some nuance where the two phrasings don't have exactly the same meaning, but I can't pin it down even in my speech. What does everybody else think?

***********

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Comments

[hamsterwoman]

, "I don't know that something or other" and other times I say or hear "I don't know if something or other".

To my mind, "I don't know IF" is genuinely not knowing/wondering, and "I don't know THAT" is a way of expressing doubt (i.e. "I suspect probably not", but not strongly). But I'm really curious to see what other people think.

[hilarita]

I think so too.

[mtbc]

Me too!

[archangelbeth]

Me three!

"I don't know if we're getting a new car this year." (Dunno! It's a possibility!)

"I don't know that we're getting a new car this year." (Whoever is talking like it's a possibility is almost certainly mistaken.)

[fox]

Yes, this.

[pauamma]

Likewise, in my idiolect.

[cosmolinguist]

This might be a difference between relative clauses (which are extremely common and normal in English and very often use "that") and the subjunctive mood (which is kind of a fossil and it's not well-understood or consistently used in modern English, but it often uses "if").

The subjunctive is (supposed to be) used for hypotheticals, to express things like wishes, demands, anything we think could or should happen. So like "If I were a rich man," the reason that phrase uses "were" for a singular subject is because it's in the subjunctive. You get "if" in a lot of wishes/speculations/hypotheticals, which is why I think it might be relevant here.

[greghousesgf]

The only name twin I had who was close to well known was a 500 pound murder victim.
I like the illusion cakes.
I've been doing D&D alignments on all kinds of stuff for years, for example, the MST3K bots are chaotic neutral.

[ioplokon]

Subjunctive (if) vs indicative (that). We've ditched our modal verbs for the most part, so it has to come through other ways.

[cosmolinguist]

I don't know what you mean by modal, but English has plenty of them: will, can, could, must, may, etc.

[marahmarie]

*Please* don't make me break out "I don't know that that is correct". But I don't know that it is or not.

To me it's informal vs. correct, ie I can't commit to "informal vs. formal", only that "if" meets the definition of what one might should say.

And now I've had too much fun.

ETA: after typing the above but before posting I googled [if or that]. Top result: a prescriptivist yelling about this in CAPSLOCK. Hmmmm.

[conuly]

Capslock. A sure sign that the prescriptivist is wrong, as always.

[marahmarie]

Oh, check this out. I was ETA2ing as you replied:

"ETA2; I re-read the prescriptivist just now and realized we prolly shouldn't take advice from them anyway, not with this opener:

"From my experience, about 95% of english speaking people (even educated people) employ this grammar (which I believe is incorrect, based on my school training in English, many moons ago, and which I hence detest and just cannot and will not adjust to !):"

I mean, what IS that? Comma after "experience". "English": lowercased, not compounded by using a dash with "speaking". End parenthese should come after the phrase "many moons ago". Exclamation point: double-spaced after the last word (that's not my typo; it's theirs). Colon used without indicating why.

And why can't "employ" just be "use" and "school training" be "what I learned", anyhow?

And this from a) a proofreader who b) yells at the rest of us ("about 95%" - love to know where they pull this figure from!) over how we use English."

[conuly]

Wow, it's worse than I thought.

[marahmarie]

Come to think of it, their second parenthetical thought isn't even parenthetical, it could've stayed part of the sentence without breaking the flow or meaning, and I need to stop reading this paragraph as if I pick it apart much more it might simply cease to exist.

[gale_storm]

Okay, I’m giving all the rest a wide enough (I hope) berth, but I just wanted to thank you for providing all of these linky bits on a regular basis. Some I’ve had coming to me already, but it’s good to get a little revivifed peek at them. Others are new to me entirely and are all the more welcome.

[rhoda_rants]

I personally have been washing my hands to the chorus of "No Scrubs" by TLC.

[mme-n-b.livejournal.com]

I say "whether " :)

[conuly]

So long as I know whether there will be weather.

[mme-n-b.livejournal.com]

Yup :). And I pronounce both “vetherrr”

[elenbarathi.livejournal.com]

Hmm, okay, I'll have a go. There IS a subtle distinction, and it rests on how credible one finds the original statement. If I say "I don't know if (or whether) that is true", what I mean is "I honestly don't know whether that is true or not." However, if I say "I don't know that that is true," what I mean is "I think that is NOT true, but I don't know for a fact that it's not."

[conuly]

This is the consensus I'm getting, thanks :)