Halliday (2008: 97):
[Grammatical metaphor] is functional [in theory-building] in two distinct though complementary ways.
- On the one hand, it creates technicality. The virtual entities that come into existence through semantic junction embody a large amount of technical knowledge; and these technical terms can be organised into technical taxonomies thanks to the constructional resources of the nominal group.
- On the other hand, it creates rationality. In the same way, by “packaging” a lot of previous information in the text, the nominalisation makes it possible to build up chains or sequences of logical argument; these are construed by the text-forming resources of the grammar (in English, the organisation of the clause into Theme and Rheme, and of the information unit into Given and New.)