How does the parenthetical "that is" function?

Question

Question 1:

An excerpt from The Economist:

China’s kingmakers may have decided to play safe for now, but leadership issues will again loom large in 2017 when the party’s next five-yearly congress is due to be held. By then the newcomers to the standing committee will be considered too old to carry on. Some of the powerful elders might have faded from the scene. Mr Xi and Li Keqiang might then have a freer hand to promote their own people, and perhaps more daring ones. If, that is, they manage to keep control until then.

I know that the last sentence of means "it is possible only if they manage to keep control until then" or "it's impossible unless they manage to keep control until then".

But I don't understand how the sentence functions: what does "that" refer to, or is it just an empty word refering to nothing in particular?

Question 2:

It is not until 3am that they returned home

I think that "it" refers to the fact that "they returned home", and that the above sentence can be rewritten as "the fact that they returned home is not true until 3am." This sounds wierd but has helped me to understand the sentence's functioning. But some people tell me that I shouldn't comprehend the sentence this way because "it" doesn't refer to anything. Am I really wrong in my understanding of "it" in that sentence? If so, how do you think I should understand it?

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EDIT

So everybody thinks that is is short for that is to say? But I really think that it means anything but that is to say. Before I asked this question I had tried to comprehend it that way, and noticed an absolute logical error: since that is to say usually connects two grammatical constituents expressing a similar meaning, the two constituents should be of the same pattern. That is to say, if the previous constituent is a statement, then the following one should be a statement as well in spite of all its clauses and parentheses. But in the above excerpt, that is is linking a conditional clause with a full sentence.

Answer 1

I strongly suspect that that is was coined as a literal translation of the Latin expression id est (i.e.) with the same meaning, because the construction makes more sense in Latin.

Originally, that is (to say) was used at the beginning of a sentence, where that referred to the previous sentence, or between the two sentences, just like i.e.:

The first Roman Emperor was Gaius Julius Caesar. That is, he was the first man who ruled the Empire de facto single-handedly, though he was no emperor in name.

In later use, its position has tended to shift around a bit, but it still refers back to the previous sentence or an idea expressed therein.

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Your analysis of it is perfectly fine. You could say it is the subject and the that clause an appositional complement to the subject.

This did not happen until 3 am, (namely) the fact that they returned home.

It is of course a fixed idiom, so that the internal structure doesn't matter a great deal any more. Note that it is used in many languages, like French c'etait là que..., Dutch het was daar dat... = "it was there that...".

Answer 2

A previous statement is made. It is given the follow-up statement that indicates the statement is only possible if another condition occurs.

I'm going to the movies tonight. If, that is, my car ever gets out of the shop.

Answer 3

If, that is, they manage to keep control until then.

The that is a pronoun referring to whatever is stated earlier, probably immediately prior in the previous sentence. The placing of "that is" after if serves to emphasise the "If" and the improbability (in the author's view) that they will "keep control until then".

It was not until 3am that they returned home.

Here the it is a dummy which is there to provide a subject for the verb. It's the complement which is important — they did not return home until 3am. It in that sentence does indeed mean nothing, and the sentence has a similar (but not absolutely identical) structure and analysis to "It is raining".

Answer 4

That is (to say) is used to give more details about something, with that referring to whatever was just said and with an elaboration following the phrase.

Answer 5

Pronouns do not always refer to something else identified in the text.

Sometimes pronouns are exophoric and refer to something extralinguistic:

That is John's. [Speaker points to a book belonging to John, establishing a referent.]

Sometimes pronouns are homophoric and refer to something known only through context:

He is risen. [Spoken in a Christian church, establishing the referent as Jesus.]

Sometimes pronouns are expletive, or dummies, and have no referent. They are required by functional syntax have no semantic meaning.

There are seven continents. [The usual way of stating 'Seven continents exist'.]

Finally, some pronouns appear in idiomatic expressions and have no referent but contribute to a construction that has semantic meaning:

John was really out of it. [In the sense of 'John was dazed and confused'.]

In this last case, it is not fruitful to ask "John was out of what?". There is no referent for the 'it' in 'out of it'; 'out of it' is a construction with a meaning of its own. The same situation applies to 'that is' in the sense of 'i.e.': there is no referent for "that", it's just part of the phrase.

Answer 6

The question may be understood, and I believe, answered better with the addition of further context. This was the source excerpt:

China’s kingmakers may have decided to play safe for now, but leadership issues will again loom large in 2017... Mr Xi and Li Keqiang might then have a freer hand to promote their own people, and perhaps more daring ones. If, that is, they manage to keep control until then.

It may have been easier to understand if the last two sentences were combined into something like this: "Mr Xi and Li Keqiang might then have a freer hand to promote their own people, and perhaps more daring people, presuming they manage to keep control until then." or "subject to whether or not they keep control until then". The problem with my alternative is that it reads awkwardly, and is unnecessary verbiage for anyone who is fluent in the English language.

The phrase "If, that is" was a nice stylistic choice, in terms of composition. It imparts a tone of uncertainty that is suitable for the conjectural and slightly dramatic nature of the subject matter. This is an important event on its own, and in an historical context, based on the preceding content of the article. It could have been expressed as

If, that is to say, they manage to keep control until then.

Another answer, by @Cerberus alluded to that as well, although I don't believe that id est, commonly abbreviated as i.e. would have been appropriate here (@Cerberus did not claim that it would be).

Your other question was about this sentence:

It is not until 3am that they returned home.

First, I believe that it should be: "It was not until 3 am that they returned home." Otherwise, your understanding seems correct to me. That is to say, "it" refers to the act of returning home. The action did not take place until 3 am.

• That was a fine article you referenced in The Economist. It was very informative. Thank you!

Answer 7

“that is to say” usually connects two grammatical constituents expressing a similar meaning

Although the phrase “that is”/“that is to say”/“i.e.” is commonly defined as suggesting equivalence, in practice, its logical flow actually runs the gamut:

1. ⟺  (“in other words”, clarification)

   • The sinks of homes with hard water—i.e., a high mineral content—will gradually accumulate white or yellow buildup.

   • Triangle A is equilateral; that is, its sides are of equal length.

2. ⟸  (clarification, elaboration)

   • One meal, i.e., breakfast, is included in the price of the room.

   • One of the intercepts of the line y=x+3, that is, its x-intercept, is negative.

3. ⟹  (elaboration, “in other words”)

   • You’ll love how your face feels with the new Guide-n-Glide razor; i.e., it will feel handsome, fresh, and clean.

   • Figure A is equilateral triangle; that is, its sides are of equal length.

leadership issues will again loom large in 2017. Mr Xi and Li Keqiang might then have a freer hand to promote their own people, and perhaps more daring ones. If, that is, they manage to keep control until then.

what does “that” refer to, or is it just an empty word refering to nothing in particular?

The word “that” refers to its preceding sentence “Mr Xi and Li Keqiang might then have a freer hand to promote their own people, and perhaps more daring ones”.

The entire phrase “that is” is functioning as a parenthetical side comment, and means “more precisely” (this meaning corresponds to sense #2 above).

And, as pointed out by Andrew and Ellie, the phrasing “…—if, that is,…” emphasises the hypotheticality of the foregoing conjecture.

So everybody thinks “that is” is short for “that is to say”? I had tried to comprehend it that way, and noticed an absolute logical error: in the above excerpt, “that is” is linking a conditional clause with a full sentence.

The phrase “that is” is actually implicitly linking two full sentences in the excerpt, which can be pared down and rearranged as

• They might in 2017 have a freer hand to promote their own people and perhaps more daring ones. That is, if they manage to keep control until 2017.

then expanded (please pardon the contrived phrasing) as

• They might in 2017 have a freer hand to promote their own people and perhaps more daring ones. To clarify / More precisely: they might in 2017 have a freer hand to promote their own people and perhaps more daring ones if they manage to keep control until then.