Martin (1992: 401):
With notable exceptions (e.g. Halliday 1984) Halliday's work on English content form has generally assumed an unstratified system/structure cycle organised by rank and metafunction.
This is a very serious misrepresentation. The stratification of the content plane into two strata, semantics and lexicogrammar, has long been at the very heart of SFL theory — not least because the notion of grammatical metaphor depends on it — and long precedes the work of Halliday's students, such as Martin (1992). For example, in the work most cited in Martin (1992), Halliday & Hasan (1976: 3) write:
Language can be explained as a multiple coding system comprising three levels of coding, or 'strata': the semantic (meanings), the lexicogrammatical (forms) and the phonological and orthographic (expressions). Meanings are realised (coded) as forms, and forms are realised in turn (recoded) as expressions. To put it in everyday terminology, meaning is put into wording, and wording into sound or writing…
The stratification of content, cross-coupled with the distinction of paradigmatic and syntagmatic axes, produces two system–structure cycles, one on each stratum. Halliday & Matthiessen (1999: 429):
…in our model there are two system-structure cycles, one in the semantics and one in the lexicogrammar. Terms in semantic systems are realised in semantic structures; and semantic systems and structures are in turn realised in lexicogrammatical ones.It is another of Halliday's students who proposes a single system–structure cycle, though with a stratified model of content. Halliday & Matthiessen (1999: 429):
In Fawcett’s model, there is only one system–structure cycle within the content plane: systems are interpreted as the semantics, linked through a “realisational component” to [content] form, which includes items and syntax, the latter being modelled structurally but not systemically…The importance of modelling content as stratified in SFL theory cannot be overstated. For example, Halliday & Matthiessen (2004: 25):
The stratification of the content plane had immense significance in the evolution of the human species — it is not an exaggeration to say that it turned Homo … into Homo sapiens. It opened up the power of language and in so doing created the modern human brain. …Halliday & Matthiessen (1999: 604):
This deconstrual of the content plane into two strata … is a unique feature of the post-infancy semiotic, corresponding to Edelman’s (1992) “higher–order consciousness” as the distinguishing characteristic of Homo sapiens.