[...] We shall incorporate into the grammar the notion of congruence. Language has evolved in such a way that our interpretation of experience (thinking with language) and our interpersonal exchange (acting with language) are coded into semantic structures that are plausible; and with these has evolved a lexicogrammar system that extends the plausibility principle one step further, so that even at one remove we can see (or feel; the process is an unconscious one, until linguistics begins to meddle with it) the sense that lies behind the forms.
- Halliday (1985), a pag.XIX