Text As The Process Of Instantiation

Halliday & Matthiessen (2004: 524-5):

The system of language is instantiated as text, the two representing the poles at either end of the cline of instantiation.  System and text are not different phenomena; they are phases of one and the same phenomenon.  When seen up close, this phenomenon appears to us as text; but when we adopt a more distant observer perspective, we can build up a picture of it as system.  System and text form a cline rather than a dichotomy, because between these two poles there is a semiotic region of intermediate patterns (conceived of as instance types — as text types, or as subsystems — as registers).  Text is thus the process of instantiation; and we can characterise it by reference to the system as the selection of systemic options unfolding through time.