Halliday & Matthiessen (1999: 416):
We can identify two main traditions in Western thinking about meaning (see Halliday 1977):
(i) one oriented towards logic and philosophy, with language seen as a system of rules;(ii) one oriented towards rhetoric and ethnography, with language seen as resource.
… Our own work here falls mainly within the second tradition — but we have taken account of the first tradition, and the general intellectual environment in which versions of our meaning base are being used also derives primarily from the first tradition. Indeed the two traditions can in many respects be seen as complementary, as contributing different aspects to the overall picture. Our own foundation, however, is functional.