Halliday & Matthiessen (1999: 546-7):
In the world of classical physics, the flux of experience was held under control: reality had to be prevented from wriggling, while it could be observed and experimented with. The control over experience is partly a physical matter; but it is also in part semiotic, and the semiotic control of experience is achieved by the nominalising power of the grammar. Since it is the grammar that has construed it in the first place, the grammar is able to transform it by reconstruing it in other terms. Grammatical metaphor played an important rôle in shaping our humanist world.