The inner ‘world of consciousness’ is, of course, the domain of sensing, construed by the grammar as mental processes.
As you know, Halliday & Matthiessen (1999: 143-4) situate types of sensing topologically, with cognition and desideration central, and perception and emotion peripheral — perception between cognition and doing-&-happening (behavioural processes), emotion between desideration and being-&-having (quality ascription).
Cognition and desideration are central because they alone create ideas (Halliday & Matthiessen 1999: 138). It is they that constitute interior symbolic — that is: ‘conscious’— processing (Halliday & Matthiessen 1999: 129-30).
And it is the central sensing contrast between the two modes of projection, cognition (‘I think’) and desideration (‘I want’), that constitutes the ‘inner’ dimensional contrast in this model of protolanguage.