Halliday & Matthiessen (2004: 656-7):
Nominalising is the single most powerful resource for creating grammatical metaphor. By this device, processes (congruently worded as verbs) and properties (congruently worded as adjectives) are reworded metaphorically as nouns; instead of functioning in the clause, as Process or Attribute, they function as Thing in the nominal group. … What the happens to the original ‘things’? They get displaced by the metaphoric ones, and so are reduced to modifying these…