One of us is wrong, aren't we?

Solution 1:

I've bundled up my comments into an answer of sorts. (ha, it looks worse than the comments - who chose these colours and fonts?)

In British English (or rather in Britain) I've certainly heard aren't we etc used in that way. Whether it is right/proper/by the rules/grammatical/whatever I have no idea .

One of us is wrong, aren't we?

It's got a question mark, but it's not used as a question, it's used as a statement and that particular statement means You are wrong but I'll leave it to you to tell me that it is you who is wrong.

That format is commonly used in a condescending manner or when talking to children.

One of us was breaking the speed limit, weren't we Sir?

meaning You were breaking the speed limit.

One of us is heading for a smack, aren't we?

meaning You will soon get your bottom smacked if you don't stop what you are doing

And in the case of the original question

One of us is going to have to start talking, aren't we?

meaning I'm going to start talking but I've said this in an introductory fashion so as not to appear too forward

But then, there's the balls...

One of these balls is blue, isn't it?

Is pretty standard I'd say, it might be rhetorical or it might be a proper question that needs an answer to someone learning colours.

It could even be a test for someone who has difficulties with words and/or the balls are actually red and green.

This version however

One of these balls is blue, aren't they?

I don't think I've ever heard a question posed like that (in BrE).

Lengthy further discussion on comments summarized here just in case a raft of comments get deleted, but we all know that never happens, don't we?

Can we use One of us is wrong, isn't he? without any sarcastic or patronizing undertone? Just as in Well, we can't both be right, so surely one of us is wrong, isn't he?

Is there sarcasm in well, at least one of us dodged that bullet, didn't he? Am I correct is started to wonder about a specific idiomatic use of aren't we that has nothing to do any more with the actual normal formation of question tags

If you said One of us is wrong, isn't he? who would be the he in that sentence? If there are only two of you, then calling the other person he instead of you is wrong, it should be one of us is wrong, aren't you? which is quite blunt. If there were three of you, you could ask the third party One of us is wrong, is it him? not quite so blunt but not quite as clear as the simple Is he wrong?

The aren't we on it's own isn't enough to add the sarcasm. In combination with the statement the aren't we means and I (the speaker) know who that is going to be. So it's sarcastic when used with one of us is wrong but not sarcastic when used with one of us is going to have to speak first.

One of us is wrong used with aren't we has almost always got a sarcastic undertone. Without sarcasm it would just be We're wrong or One of us is wrong or One of us is wrong but I don't know which. In that particular phrase I would always assume the aren't we is sarcastic. It's a very fine line though and the intonation of the speaker is very important.

Can this irregularity also appear with or the singular subjects that get a plural question tag? And does this ever happen anywhere else than in question tags? Is "One of us is wrong. He should apologize." also wrong?

That's slightly different. You could just about say that to a third party (imagine two children A & B are arguing and talking to their mum). Those two sentences (spoken by A) are suggestive that A thinks B is wrong and adds He should apologise to add emphasis to their belief that B is wrong. If it were only two people then it would be completely wrong to say that, you would never address the other person as He.

However, in the UK if you were stopped while driving by the police they would always ask Have we been drinking tonight Sir? They use the we to mean you in the same way the we is used as you in One of us is wrong, aren't we? which really means One of us is wrong, aren't you?

Tip : Never answer the policeman's question with I don't know, have you been in The Bull and Bush sinking pints for the last eight hours too?, sarcasm only works one way with the police.

An example with no sarcasm whatsoever

One of us is going to have to work tonight, aren't we? That's not sarcastic if one of you does have to work tonight and neither of you know which one it'll be.

And the application of sarcasm

If you DO know it's your friend that has to work you can say One of us is going to have to work tonight, aren't we? that's sarcastic.

And in a not sarcastic manner to avoid a blunt statement

Similarly a boss could easily say to a worker One of us is going to have to work tonight, aren't we? and both parties know it means You (the worker) are going to have to work tonight. That's what I mean about it being a statement and not a real question.

It's definitely a 'trick' used to avoid saying a blunt statement or to give someone the opportunity to admit to something without it appearing forced so perhaps it is only used with 'questions' but as seen above it can be used in a direct meaning where two people are unsure of the outcome.

I'm not sure how different it is in AmE but I'll say that the Americans I know have no problem with this form but they are used to hearing it so they aren't a good test for BrE/AmE differences.

Solution 2:

In American Standard English, all of your example sentences sound awkward, bordering on wrong,¹ but people will still understand the meaning. The natural way for me to express these statements would be without a question tag at all — here are two variations on each, differing in nuance:

Isn’t one of these balls blue?
Shouldn’t one of these balls be blue?

and

Isn’t one of us wrong?
One of us must be wrong.

However, consistent with your intuition, the sentences with the plural question tags sound more wrong to me than than those with singular question tags. One of the easily noticeable differences between (Standard) American and British English is that British prefers plural forms in several places where American prefers singular, e.g. The committee have decided (Br) / The committee has decided (Am) — possibly this is another of those places. [EDIT: It has been pointed out in the comments that this is incorrect. Unfortunately, this leaves me with no explanation for your friend's contrary intuition.]

¹ descriptivist’s “wrong” = “native speakers would not say it that way even for stylistic effect”

Solution 3:

As a native speaker of American English,

One of these balls is blue, aren't they?

sounds definitely wrong. My explanation for why it feels wrong is that the core of the subject is One, which is singular. The prepositional phrase of these balls doesn't change the grammatical number of the subject. Compare:

Isn't one of these balls blue?

= One of these balls is blue, isn't it?

vs.

Aren't two of these balls blue?

= Two of these balls are blue, aren't they?

Solution 4:

How has nobody used the phrases Royal We or Nosism yet? Simply put they mean you can refer to oneself using we. These ideas work in many languages, however in British its use can be bastardised to add sarcasm to patronisingly or disdainfully refer to the second party. This is often accompanied by a difference in authority between the two parties, said by the higher of the two, lending a rhetoric or accusatory tone.

It is still treated as a plural by verbs so yes, your use is correct.

One of us is wrong, aren't we?

Actually implies:

You are wrong and we both know it.

It does not work with inanimate objects. Your balls and cars and whatsits are all going to be its.

Note that it can also be used as a polite form (I'll nab Wikipedia's examples) but only in certain circumstances, usually in question.

Aren't we looking cute?
How are we feeling today?

These technically show the same level of patronisation but they also imply positive opinion and care. It wouldn't be hard to turn the second into something quite malevolent:

We're feeling fine, aren't we?

Which goes back to the original answer...