CGEL by Huddleston & Pullum (Page 1537) has this example

(d) So as head of clause with dependent modifiers or complements

[64] ii The Coo-ee cordial factory prospered almost at once, so much so that my father bought a new house at Coorparoo.

And at the bottom of the next page, CGEL calls so in [64] a pro-form as follows:

In [64] so is the head of a clause; clauses normally have a verb as head, but so lacks the important inflectional properties of verbs. Overall, then, we prefer to classify anaphoric so simply as a pro-form; its properties are unquestionably unique, and we do not believe that anything is gained by forcing it into one or more of our general part-of-speech categories.

Now, two pages later, CGEL has this example:

[72] iii There had been a power failure, so that all classes had had to be cancelled.

In [72iii] so is a preposition functioning as head of a result adjunct.

I wonder how and why you should distinguish the two so's as in CGEL. If so in the first example is a pro-form, shouldn't so in the second example be a pro-form, as opposed to a preposition?

  • 4
    They're different entities. 'So much so [that]' means 'to the degree [that]'. 'So that' means 'with the result that'. Oct 4, 2017 at 8:10
  • @EdwinAshworth Doesn't so in so that refer back to the main clause?
    – JK2
    Oct 4, 2017 at 8:14
  • 1
    Collins labels so that a [compound] conjunction expressing [almost always] purpose. I did X so that Y would happen. Oct 4, 2017 at 8:28
  • There are a lot of idiomatic compounds. I remember a paper by (I think) Lakoff and Ross called "A criterion for verb phrase consistency, or Why you can't do so into the sink", which contrasted differential behaviors of the verbal anaphors do so, do it, and do that. Very early generative semantics, lots of data. Oct 12, 2017 at 15:10
  • I'd have said the same as Edwin already did Oct 17, 2017 at 22:28

3 Answers 3


Example 64

[64] The Coo-ee cordial factory prospered almost at once, so much so that my father bought a new house at Coorparoo.

In the sentence above the word so is taking the place of a clause. If we reinsert the clause in place of so, it will read:

The Coo-ee cordial factory prospered almost at once, so much did the Coo-ee cordial factory prosper that my father bought a new house at Coorparoo.

[Notice here that the clause following that is not related to the so that we replaced. It is a dependent of the initial degree adverb so at the very beginning of the clause. The sentence is similar in structure to:

  • So fast did it go that we could not catch it.]

Example 72

There had been a power failure, so that all classes had had to be cancelled.

Here the word so does not represent a clause. In fact it is appearing between two clauses:

  • [There had been a power failure] so [that all classes had had to be cancelled.]

The word so here belongs with the second subordinate clause, of which it is the head. This so is different from the one in (64). In (64), the pro-clause so was not related to the clause following it. We showed that, in fact, the clause following so in that construction is actually a dependent of the earlier degree adverb so. However here, in example (74), the following clause is directly related to the word so. This is because the word so tells us that the classes being cancelled is a result of what was described in the main clause.

The so in (74), therefore, is a very different beast from the one in (64). Nonetheless, it still has some similarities. Apart from sounding the same, both have an anaphoric relationship with what has been said before. However, in (74), the word so is not a pronoun, pro-verb, or pro-clause. It is merely a resultative preposition.

  • In your last paragraph, you say "both have an anaphoric relationship with what has been said before". Isn't such an anaphoric relationship what makes a form a pro-form? You've already acknowledged that it's a pro-form and then claim that (74)'s so is not a pro-form, so that you've lost me there.
    – JK2
    Oct 17, 2017 at 17:31
  • @JK2 I get what you're angling at, but no, not exactly. Let me try and explain why (I'm not sure I'll succeed!). A pro-form carries out a syntactic job in a sentence (like being a Subject, or a Direct Object, or a Modifier). It differs from other groups of words that can do that job by a) not having a fixed meaning or referent, and b) by usually standing in for a whole phrase or clause instead of just a word (so for example, pronouns stand in for whole noun phrases, not just nouns). Whilst pro-forms are often deictic in some sense ... Oct 17, 2017 at 21:16
  • @JK2 ... (they can be anaphoric, referring backwards, or cataphoric, referring forwards, or exophoric, referring to something outside of the immediate discourse), this doesn't mean that all deictic words are pro-forms. So for example, however normally contrasts what's coming next with what has been said before. But we don't interpret however as standing in for another group of words interpretable from the context. And but, in some sense, can be thought of as relating what is coming with what has gone before without standing in for previously mentioned words. ... Oct 17, 2017 at 21:22
  • @JK2 ... Similarly, resultative so doesn't syntactically stand in for a group of words even though it contrasts what came before with what's coming up next. You can't replace resultative so with another phrase that came earlier. In contrast, pro-clause so actually does the same syntactic job as the clause (which you can reconstruct from the context) would do. I don't know if I'm being very clear? Oct 17, 2017 at 21:27
  • If you still think that (74)'s so has an anaphoric relationship with the foregoing clause, I don't understand why (74)'s so cannot pass muster as a pro-form if it can be thought of as a) not having a fixed meaning or referent and b) standing in for the whole preceding clause. OR can it never be thought of as such?
    – JK2
    Oct 18, 2017 at 1:44

The key to understanding so that and so much so that lies in grasping how many roles "so" can actually play, and identifying which role(s) it plays in the expressions you are considering.

In the Wiktionary entry, there's an etymology drawing on multiple European languages. However, there's also parallel usage in French (tel, tellement) and the sound itself occurs in other languages that have influenced English in other ways, such as Japanese.

The general usage of so is to refer to something that has already been established between two speakers, or between the writer and the reader, as in Jean-Luc Picard's well-known "Make it so" from Star Trek.

In the Wiktionary entry, so is first characterized as a conjunction and as an adverb, but examples of its other uses are given later.

The key to identifying the role of any given so is to transform the expression by replacing so with a more specific word or set of words that convey the same meaning. For example:

  • so = "I accept what you just said, and the consequence will be what you say next." Essentially a conjunction, like therefore. If you can replace the so with therefore, you have narrowed down its role. It can be a conjunction uniting two related but independent actions, or the introductory word in an adverbial clause, which modifies the first action (the Wiktionary gives therefore as an adverb).

  • so that is almost the same as so, since in most English expressions that can be eliminated without changing the meaning. In practice, however, so that connotes purpose. Compare:

    • The air cooled, so the leaves changed color. Conjunction. Replacing so with and does not change the meaning (very much).

    • The farmer placed nets below the trees, so that the apples would be caught before they reached the ground. Adverb identifying the goal of the first action. Replacing so with and changes the meaning by de-emphasizing the will of the farmer. Replacing so with in order that or with the purpose of keeps the meaning intact.

  • so much so that: an expression that introduces an adverbial clause by referring to two previously expressed ideas. It's probably best to view this as an idiom that allows you to make these references conveniently. For example: in The Coo-ee cordial factory prospered almost at once, so much so that my father bought a new house at Coorparoo, we have:

    • the first so refers to the verb prospered, but it plays a double role as an adverb for the so that follows. You could replace so much so that with so remarkably that and keep the meaning.

    • the second so refers to the adverbial phrase almost at once. You could replace it with better than his competitors and still have a meaningful statement.

    • much is functioning as an adverb modifying the second so. You could replace it with ridiculously, i.e. ...prospered almost at once, so ridiculously so that my father bought...

As a further example, we could imagine a Jean-Luc Picard saying: "Make it so. So much so that these creatures never return to this part of the Galaxy again."

So the challenge with identifying so as a part of speech is that the prior reference is sometimes hard to infer. So perhaps it's best to think of expressions with so as special cases of conjunctive propositions introducing adverbial clauses.

Finally, don't forget that CGEL offers a somewhat narrow academic perspective on our language, and that there's actually quite a lot you can say with so, e.g.

  • Alphonse: And so?

  • Gaston: So, since you so want to know, Miss So-and-so lives in that so-so district that we keep hearing so much about. So just let it be, okay?"

  • Alphonse: Oooh... soooo intense. So tell me how come, huh?


The easiest way would be to isolate the antecedent, i.e. what so actually refers to.

[64] ii The Coo-ee cordial factory prospered almost at once, so much so that my father bought a new house at Coorparoo.

refers to the verb "prospered": "he prospered... so much so", i.e. "to such a degree".

As Collins nicely states "If you say that a state of affairs is so, you mean that it is the way it has been described. " So is adverb ("it is so"), and *so much so" an adverb group.

The construction is so much so + that.


There had been a power failure, so that all classes had had to be cancelled.

Here so that has become an inseparable idiom (conjunction) that refers to no word in particular in the previous clause, but to the clause itself ("with the consequence that"). It can also be noticed that there is no idea of degree, the logic is binary (power failure => cancellation).

In truth it's not fundamentally different, but merely a semantic shift: the word so has lost its own individuality as an adverb, and it is now agglutinated to that, forming a single unit that is now perceived as a conjunction.

Whichever way one wants to call this technically, the difference should appear obvious.

  • Just because the two so's are 'different' does that mean the two so's should always be different parts of speech?
    – JK2
    Oct 18, 2017 at 2:26
  • I guess the answer would be "it depends". Does it really matter? A "part of speech" is essentially a technical rationalization of how words are being used in everyday usage or in written language. Sometimes there is an element of convention and even of arbitrary in grammatical descriptions (one choice has to be made, and one convention has to prevail). I find it easier to go below the level of conventions and understand what is really going on, and why it happened (see Feynman's remark that names don't constitute knowledge).
    – fralau
    Oct 20, 2017 at 16:56

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