“I.e. there's a sense in which the writing does itself, or perhaps that when we write we're in a partnership with something else that's got its own ideas.” (Blog posting, 9 February 2009)
That something else is of course the language. What the language gives us is not just words (with all their associations, triggerings, resonances) but also runs, moves, lines, approaches, rhythms, progressions. It gives us packages, partly of constellations of ideas and meanings, partly lexical, prosodic etc – the sorts of vocabulary and sorts of rhythm that go with the theme.
Yes, as is mainly stressed these days, we get these resources from genres – genres give us ways of going about things. But the resources are often found in more than one genre; (b) genres aren’t as determinate as often made out and (c) despite the myth in some versions of English, we often don’t write in determinate genres, though genres always exert a pull on our writing: we manoeuvre amongst them, sometimes lining ourselves up completely with one, sometimes merely alluding to one by in passing.