Halliday & Matthiessen (1999: 271, 272):
Thus grammatical metaphor is a means of having things both ways. An element that is transcategorised loses its original status because of the nature of the semantic feature(s) with which it comes to be combined (e.g. 'like ...' is a quality; so when we say mousy 'like a mouse' this is only a quality — it has none of the thing-ness of the original mouse). A element that is metaphorised does not lose its original status. Its construction is not triggered by its being associated with any new semantic feature. If it has a new semantic feature this is as a result of the metaphorising process. So failure is both process and thing: it is a process construed as a thing (or rather, a phenomenon construed as a process and reconstrued as a thing); its initial status as process remains, but because it has been nominalised, and the prototypical meaning of a noun is a thing, it also acquires a semantic status as something that participates in processes: see Figure 6-4. It has become a 'junctional' construct, combining two of the basic properties that the grammar evolved as it grew into a theory of experience.
