Halliday & Matthiessen (1999: 599):
These two models move away from the folk model in two directions.
(i) They reinterpret figures of sensing as figures of doing or being-&-having; that is, they interpret mental phenomena in material terms. With the growth of cognitive psychology, this situation has changed, of course; it is no longer disallowed to talk about mental processes.
(ii) They emphasise motivation as an important unconscious psychological factor; thus they introduce unconsciousness in the account of the workings of the human mind. In the systems of process types in the grammar, there is no 'unconscious' type of sensing distinct from the conscious ones that can project ideas.
In a way, the two directions away from sensing … in the unconscious folk model — material reinterpretation and 'unconsciousness' — are opposites: the first reconstrues sensing in terms that are more readily observable by scientific method (i.e., method other than introspection), while the other introduces a factor that is even less readily observable than conscious sensing: unconscious motivation. But they share the characteristic that they construct the 'mind' as remote from our everyday experience with sensing.