Robbie says below that people thinks about the fundamental/derivative distinction in such different ways. One truthmaker for this claim is the pair of him and me! At least, maybe: we've been talking about this stuff, and I'm not entirely sure about whether we do in fact disagree substantially. Anyway, I thought I'd also post my current thoughts on the matter. This is *extremely* work-in-progressy, and a lot of work needs to be done, so comments are very welcome.
My paper is here.