Choice, system, realisation: Describing language as meaning potential

…in linguistics language is turned back upon itself. We have to use language about language, words about words, letters about letters. (Firth, 1957:121) Introduction Choice’ is a ‘common word’ borrowed to function as a technical term in Halliday's Systemic Functional Linguistics (SFL). However, the continued use of common words in the realm of theory alters their semantic identity: they put away things non-theoretical, and their meanings are largely governed by the co-ordinates of the theory, with the word's value and signification becoming equally virtual. The ‘things and relations’ they refer to represent ‘constructs’ that ‘have no ontological status…They are neither immanent nor transcendent but just language turned back on itself’ (Firth, 1957:181; also Halliday, 1984a). Ideally then, technical terms should perform some precise functions demonstrably essential to the theory's working: in fact, their validity can be judged only by the work they do in construing a model of language (Halliday, 2002d; Butt, 2005; Butt & Wegener, 2007). But the reverse is just as true: a theoretical term is only as valid as the ‘ideas about language’ modelled by the theory (Halliday, 1976a, 1977a): I have argued (Hasan, 2012, 2013) that the SFL modelling of language has reached considerable success, which is not to claim that the theoretical profile of language has become simpler; simply that the processes of the system as identified by the theory agree with the users’ experience of it as a meaning potential: A successful theory must allow the renewal of connection with the data of experience current in the community.