Halliday & Matthiessen (1999: 545-6):
But to say that the semantic relations have become less explicit is to imply that these relations themselves have not changed. In one sense, this is true: we can "unpack" the metaphor, and experts will generally agree on how to do it. But in another sense it is not true. Scientific discourse began, as we saw, with the creation of technical taxonomies and mathematical constructs; these were already modulating the semiotic construal of experience, even if only at the margins, by creating a new realm of abstract things that had not existed before. But the transformation brought about by the renaissance was a more fundamental one; not only was this realm of abstract things greatly extended, but, more significantly, phenomena hitherto construed as processes and properties were now transformed into things — they were reconstrued, by grammatical metaphor.