Halliday & Matthiessen (2014: 30-1):
But the grammar also shows up a third component, another mode of meaning that relates to the construction of text. In a sense this can be regarded as an enabling or facilitating function, since both the others — construing experience and enacting interpersonal relations — depend on being able to build up sequences of discourse, organising the discursive flow, and creating cohesion and continuity as it moves along. This, too, appears as a clearly delineated motif within the grammar. We call it the textual metafunction.
Halliday (2008: 45):
Every clause in every kind of discourse combines an ideational and an interpersonal strand of meaning. But weaving these two together is an extremely complicated task; and in managing all this complexity, language evolved a third metafunctional component, by which it is enabled to organise itself in the form of discourse. Discourse is what linguists perceive as text; so we call this the textual metafunction. This is what enables a language to function meaningfully in all its multifarious contexts.
Halliday (2008: 142):
This blending [of the ideational and the interpersonal into a lexicogrammar] entailed a third component, that we call the textual, whereby the meanings are organised into discourse in such a way that each element in this experiential-interpersonal complex (each clause, since that is the key grammatical unit where most of the blending takes place) makes sense with its surroundings, both its material environment of what is going on around and its semiotic environment of other clauses that have gone before.
Halliday & Matthiessen (1999: 7-8):
The textual metafunction is an enabling one; it is concerned with organising ideational and interpersonal meaning as discourse — as meaning that is contextualised and shared. But this does not mean processing some pre-existing body of information; rather it is the ongoing creation of a semiotic realm of reality.
Halliday & Matthiessen (1999: 512):
Textually, the grammar is the creating of information; it engenders discourse, the patterned forms of wording that constitute meaningful semiotic contexts. From one point of view, therefore, this “textual” metafunction has an enabling force, since it is this that allows the other two to operate at all. But at the same time, it brings into being a world of its own, a world that is constituted semiotically. With the textual metafunction language not only construes and enacts our reality but also becomes part of the reality that it is construing and enacting.
Halliday & Matthiessen (1999: 528):
There is a third component in the linguistic construction of meaning; this is what we refer to as the “textual” metafunction. If we were trying to find a term to match the expressions “language as reflection” and “language as action” that we used to gloss the ideational and interpersonal metafunctions, we might come up with “language as information”; but this is itself not very informative. It is a difficult concept because unlike the other two, the textual metafunction has no obviously distinct function at the back of it. All uses of language involve the creation of text. But at the same time this is precisely the context in which the textual metafunction may be understood.
Halliday & Matthiessen (1999: 528):
… and if we observe children developing their mother tongue we can see how the ideational and interpersonal resources of the system gradually emerge from the earliest semiotic encounters, in a way which may plausibly mimic how the metafunctions originally evolved. The textual metafunction is different because it does not originate in an extrinsic context of this kind. Rather, it is intrinsic to language itself.
Halliday & Matthiessen (1999: 528):
The “textual” metafunction is the name we give to the systematic resources a language must have for creating discourse: for ensuring that each instance of text makes contact with its environment. The “environment” includes both the context of situation and other instances of text.
Halliday & Matthiessen (1999: 528):
Relative to the other metafunctions, therefore, the textual metafunction appears in an enabling rôle; without its resources, neither ideational nor interpersonal constructs would make sense.
Halliday & Matthiessen (1999: 532):
… in the course of serving this enabling rôle, the textual component opens up a new dimension of meaning potential, in that it construes a further plane of “reality” that is as it were made of language — meaning not as action or reflection but as information.
