Predicated Theme vs Postposed Subject

Halliday (1994: 60-1):

Fact vs Idea In Impinging Mental Clauses

Halliday & Matthiessen (2014: 544):

Like ‘middle mental’ clauses, ‘effective’ ones either project ideas within a clause nexus or include fact clauses as Phenomenon, e.g. 

 

The first means ‘in my opinion there’s no one here’, with there’s no one here as an idea. The second means ‘there’s no one here, and that worries me’, with there’s no one here as a fact. The fact exists prior to the occurrence of the mental process; but the idea does not – it is brought into existence in the course of the mental process. Thus the second is agnate with there’s no one here, which worries me; but we cannot say there’s no one here, which strikes me. The two are very distinct in speech, thanks to the intonation pattern (see below); the different analyses are given in Figure 7-25. 

 

The difference in structure is clear from the intonation pattern. That of (a) corresponds to I rather think there’s no one here, with falling tonic (tone 1) on here and perhaps a separate falling-rising tonic (tone 4) on strikes/think; that of (b) corresponds to it worries me, the emptiness of the place, a compound tone group with tone 1 on worries and tone 3 on here/emptiness, showing clearly that that there’s no one here is functioning as a postposed Subject. Again, it strikes me is a cognitive process clause, and so can project an idea, whereas it worries me is and emotive one and cannot.

Embedded Clause As Postposed Subject

Halliday & Matthiessen (2014: 198):

In many instances an embedded clause functioning as Subject appears at the end of the clause in which it is embedded, with an anticipatory it occurring in the normal Subject position, as in it’s no use crying over spilt milk. In such cases there will be a marked variant with the clause Subject at the beginning: crying over spilt milk is no use.

Theme Predication Vs Postposition: Embedded Fact Clause

Halliday & Matthiessen (2014: 125):

Now, one common type of these clauses is that where the postposed Subject is an embedded ‘fact’ clause. Here the pronoun substitute is always it:

it helps a lot to be able to speak the language
I don’t like it that you always look so tired

So if the postposed fact clause is introduced by that, and the matrix clause has the verb be plus a nominal, the result may look like a predicated Theme; for example:

it was a mistake that the school was closed down
it’s your good luck that nobody noticed

But these are not predicated Themes; the postposed Subject is not a relative clause, and there is no agnate form with the predication removed, proportional to it was his teacher who persuaded him to continue: his teacher persuaded him to continue. The last example is in fact ambiguous, and could be used to illustrate the difference: it’s your good luck (that) nobody noticed

(i) predicated Theme: agnate to
nobody noticed your good luck 

(ii) postposed Subject: agnate to
the fact that nobody noticed was your good luck

Theme Predication Vs Postposition: Afterthought

Halliday & Matthiessen (2014: 124):

A structure that can look superficially like Theme predication, but is not, is that involving postposition, where one nominal element of the clause – typically the Subject, though not always — is delayed to the end and the appropriate pronoun is inserted as a substitute in its original slot. This may be a nominal group, as in:

they don’t make sense, these instructions
shall I hang it above the door, your Chinese painting?
in some places they’ve become quite tame, the wombats

Here the Theme is, as usual, the item(s) in first position: they, shall + I, in some places; while the postposed nominal functions as Afterthought, realised prosodically by a second, minor tonic with tone 3:

// 1 ^ they / don’t make / sense these in// 3 structions //