Here we can briefly mention three aspects:
the complexifying trajectory From Symbolising To Sensing To Behaving To Saying,
cognition as emerging (and remaining) within semiosis, and
the experiential complementarity of sensed Phenomena.
The perspective we took enabled us to see consciousness, in the sense of perceiver-perceiving, as emerging from symbolising processes (Halliday & Matthiessen 2004: 234-5); Halliday & Matthiessen 1999: 600): symbolic identity (Halliday & Matthiessen 1999: 514) relations between material impacts on sensory detectors and the selection of neuronal groups in global mappings, with the senser emerging as the ‘meta-medium’ through which the process of ‘identifying-identifieds’ unfolds.
One point in this model’s favour is that the construal of the Senser as a “meta-medium” in this way is broadly consistent with the ‘meta’ nature of consciousness, usually phrased by philosophers as: ‘consciousness is consciousness of something’.
With the addition of ‘proto-saying’ (exterior symbolic processing) to sensing (interior ‘conscious’ symbolic processing (Halliday & Matthiessen 1999: 129, 153) through protolanguage, and the exterior projection of the microfunctional contents of consciousness, consciousness becomes more complex by being not only a process of the organism, but also the instantiation of the collective consciousness provided by social semiosis.
(And we have not even touched upon the interpersonal perspective: consciousness as enactment.)
The perspective we adopted also demonstrated
how ‘… meaning is created in other semiotic systems … such as perception’ (Halliday & Matthiessen 1999: 429)
and how cognition, as a type of sensing, emerges from such a semiotic system,
and so the sense in which ‘all knowledge is constituted in semiotic systems’ (Halliday & Matthiessen 1999: 3).
And perhaps it’s worth bringing in the interpersonal dimension of modality here, and mentioning the probability/usuality aspect of cognition (“the mind”) — and perception too, if cognition is perception in projecting (symbolic processing) mode,
which is perhaps less acknowledged than the inclination/obligation nature of desideration (“the will”) — and emotion too if desideration is emotion in projecting (symbolic processing) mode.
And the third aspect with respect to the evolution of consciousness, was the significance of the complementary perspectives on the phenomena of experience. We saw, with regard to perception, that a Phenomenon can be construed as either material or mental:
either the exterior material agent of sensing or the interior mental range of sensing
A great deal of the history of Western Philosophy has been engaged with emphasising one or other of these complementary perspectives on phenomena: exterior material or interior mental. For the latter, consider the Cartesian view of matter ‘as something only knowable, if at all, by inference from what is known of mind’ (Russell 1961: 548) — the view of Chomskyan Formal linguistics — or Berkeley’s denial of the existence of matter, maintaining ‘that material objects only exist through being perceived’ (Russell 1961: 623).
And, incidentally, if anyone asks later how emotive sensing emerges from identity relations, we will again see the same material/mental complementarity —though in this case the exterior material agents of emotive sensing are ‘visceral’ states of the body, rather than impacts on sensory cells.