Which one is correct?
The grammar rules I know say that (2) should be correct, but it feels wrong, because the statement is essentially negative (so there should be a positive question tag).
@ColinFine got it right.
I don’t suppose you are coming, are you?
*I don’t suppose you are coming, aren't you?
The second one is ungrammatical. The first one is the way it should be.
That's the answer. Here's the reason why that's the answer.
There are two clauses in the original statement, with two verbs, suppose and come (which both occur with auxiliary verbs, but they're the clausal main verbs). The second clause you are coming is the direct object of the main verb suppose, and if there were no negatives, the tag question would be aren't you?
But there is a negative; it's I don't suppose. However, whatever rules you may think you know, there's none that produce the second example. It's unusual to make a tag question with a first-person subject
but it's possible, if rare. So a tag question for
would be
which is odd (why don't I know what I suppose?), but grammatical.
The next problem is how to tag the downstairs verb. To do this you have to note that, with what are called Negative-Raising Predicates, including, but not limited to
negating the predicate in the upstairs clause is equivalent to negating the predicate in the downstairs clause. This is called Negative Raising -- the semantic result is that the negative originates downstairs and is moved to its place upstairs by rule, without changing meaning. But tags pay attention to meaning.
And, since that last sentence means I suppose you're not going, therefore a correct reversing tag of the downstairs clause is a positive , are you?
You're right. I don't suppose you're coming is essentially negative: it means much the same as I suppose you aren't coming.
“I don’t suppose, ...” makes the question that follows rhetorical. The speaker is sure that the person addressed is not coming, so the question expects a negative answer. That means it should be “are you?”
If the sentence had began, “Of course you’re coming,” making the following rhetorical question expect an affirmative answer, it would be “Of course you’re coming, aren’t you?” or, more formally, “are you not?”
If the question is not rhetorical at all, it couldn’t be introduced with a bare comma. That would be, “I hope you’re coming, but are you?” or “I don’t know whether you’re coming. Are you?”
This wrinkle has caused some older translations of the Bible to revise some verses that were translated “Is this not so?” in the 1600s to say, “This is not so, is it?” in modern English.
The OP's question suggests that one or other tag must be correct, and that the only possible source of disagreement is which of those two tags is correct.
But the OP's example sentences show a phenomenon identified by Araucaria in a comment to the question: "subordinate negation". The tags in those sentences relate to the subject and verb of the subordinate clause, "you are". But English doesn't work like that. Tags can't be used like that. Tags must relate to the subject and verb of the main clause. Compare:
You don't think it's right, do you?
*You don't think it's right, isn't it?
*You don't think it's right, is it?
As John Lawler points out, tag questions to first-person statements are rare. So "do I?" at the end of the OP's example might sound bad. But that would be because it's first person, not because it's the wrong tag. There is always another option: don't use a tag question at all.
Simply explained by my {now retired} English teacher: a question with a double negative is only ever nonsensical, Such a question is also a rhetorical statement rather than a question.
The key is the punctuation!
The statement, the question?
The statement is the assumption "I don't suppose..." The question is "are you" or "aren't you" The sentence is in two parts, both of which must always stand grammatically correct independently of each other.
The comma acts as a conjunction like "and"...
So use a conjunction instead of punctuation to understand the grammatical effect on a single sentence as a comparator.
"I don't suppose you are coming or aren't you?" makes no sense at all.
Compared with "I don't suppose you are coming or are you?" is clearer.
I don't suppose "Are you coming or not?" may be better? Punctuation is critical to understanding English correctly.
This is much more simple than some here seem to think. So much more that IMHO the Question belongs in English Language Learners, not here in ELU.
The example should feel wrong because yes, the statement is essentially negative so the query should be positive.
That's all there is to it.
When the grammar rules you know say that "I don’t suppose you are coming, aren't you?" should be correct can you either explain those rules, or rule them out?
