Halliday & Matthiessen (1999: 603):
The scientific model takes off from the grammar of mental processes (seeing, feeling, thinking) but ignores verbal processes (saying) — although the two are both processes of consciousness, are closely related grammatically, and share the critical feature of being able to create meaning by projection. … Our sense of ourselves as conscious beings comes as much from the fact that we talk as from the fact that we think and feel …