Martin (1992: 293):
On the basis of this characterisation of field, the discourse semantic unit underlying lexical item and entering into cohesive lexical relations can be set up. Since it is an experientially defined unit, it will be referred to as a message part, to bring out its metafunctional relationship with CONJUNCTION.
 The characterisation of field confuses context with language by construing field as a semantic description of social activity. That is, it violates the principle of stratification.
 This confuses the syntagmatic axis (structural unit) and the paradigmatic axis (lexical item).
 This places the higher level of symbolic abstraction (discourse semantic) below the lower level (lexical). That is, it inverts the stratification of content.
 This construes the experiential unit as something that is interrelated —cohesively, so: textually — rather than as something with internal structure; cf sequences, figures, elements in SFL theory.
 In SFL theory, a 'message' is a unit of the textual metafunction on the semantic stratum.
 This misconstrues the relation between the logical and experiential metafunctions as one of constituency. On the one hand, logical units don't consist of experiential units; on the other hand, the relation between units in complexes is not constituency but interdependency.