Halliday & Matthiessen (1999: 158):
The two models of participation that we have described in this section thus differ in degree of generality. The particularistic model construes figures into a small number of distinct types, sensing, saying, doing and being, with different participants in each; while the generalised model construes figures as all being alike, having a Process that is actualised through a Medium. These two models embody complementary perspectives on participation, the one transitive, the other ergative. Note that there is no necessary tie-up between the switch of perspective and the degree of generality: it is a feature of English that the generalised model is construed in ergative terms.