Martin (1992: 518):
It is important not to confuse the semiotic space under construction here with either of two independent dimensions; the interpersonal distinction between proposals and propositions, and the experiential distinction between activities and things.
 The 'semiotic space under construction here' (pp 508-23) is purported to be mode, the system of the textual metafunction at the level of context — though Martin misconstrues this as a dimension of register. As previously explained, this confuses contextual potential with semantic sub-potentials. That is, the confusion is along two dimensions simultaneously: stratification and instantiation.
 The 'interpersonal distinction between proposals and propositions and the experiential distinction between activities and things' are distinctions of the other metafunctions at the level of semantics. The confusion here is thus stratificational. In SFL theory, the proposal vs proposition distinction is one of speech function, whereas the "activities vs things" distinction corresponds to the elemental distinction between process and participant (Halliday & Matthiessen 1999: 177).