Halliday & Matthiessen (1999: 149-50):
There are two models of participation-in-process embodied in the semantic system of English —(i) One is particularistic: it diversifies our experience of participant interaction into four domains — doing, sensing, saying, and being.
(ii) The other is generalised: it unifies our experience of participant interaction across the different domains.Thus the system strikes a balance in the construal of figures between unity and diversity — between differentiating one aspect of experience from another and generalising over the whole. These constitute distinct but complementary perspectives.