- They are fundamentally flawed regarding both competence (bad empirical coverage) and performance (no plausible parsing model).
- Phase-theory is ill-motivated and doesn't get the job done.
I've got no qualms with the second claim. The motivation and empirical use of phases has frequently been criticized in the literature, and phases don't fare any better from a computational perspective. The memory reduction argument for phases is hogwash, phases have no discernible effect on generative capacity (neither weak nor strong), and they do not simplify the learning problem. Norbert captures the state of affairs ever so succinctly: Phases don't walk the walk [...] the rhetoric is often ahead of the results.
The first claim, on the other hand, I can't get behind at all. For one thing, it's a typical case of the cake fallacy: Every cake I've made in my life has been horrible, thus all cakes are horrible (and I'm more of a muffins guy anyways). Even if linguists haven't come up with any good representational models so far --- which I think many syntacticians would emphatically disagree with --- that doesn't mean the approach as such is intrinsically inferior to derivational ones. Now I can already see the flurry of posts about how theory construction is also a probabilistic process where previous failures of specific types of analysis make them less preferable, that the existence of a working representational account is moot if we can't find it, yada yada yada. Step back from your keyboards everyone, I'm actually not interested in arguing this point. My real worry is much more basic. The first claim implies, as is commonly done in linguistics, that there is a meaningful difference between representational and derivational accounts. Well, it turns out that this specific cake is a lie.