Halliday & Matthiessen (1999: x):
The semantic perspective enables us to emphasise four aspects of human consciousness which have been rather less foregrounded in cognitive approaches. One is that of meaning as a potential, a systemic resource which is deployed in — and ongoingly modified by — individual acts of meaning in language. […] The second is that of meaning as growth, a semogenic resource which is constantly expanding in power by opening up new domains and refining those that are already within its compass. The third is that of meaning as a joint construction, a shared resource which is the public enterprise of a collective (whereas “thinking” is essentially a private phenomenon “located” within the individual). The fourth is that of meaning as a form of activity, a resource of energy which is powered by the grammar at the heart of every language.