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A key move in Firestone & Scholl's (F&S's) impressive, skeptical review of putative top-down effects on perception is to bracket many attentional effects as “peripheral” – as working by altering the inputs to a cognitive process rather than by altering the processing itself. The deflationary thought (developed in sect. 4.5 of the target article) is that many attentional effects may be rather like turning one's head towards some interesting stimulus. Head-turning may indeed be driven top-down in ways sensitive to what the agent knows and intends. But in such cases, it seems that knowledge and intentions simply alter (via action) what the visual system gets as input. This idea is fully compatible with subsequent visual processing occurring in an inflexible, encapsulated (knowledge-impermeable) manner. To show genuine (interesting, nontrivial) top-down effects upon perception therefore requires showing that such effects impact not just the inputs but the processing itself, and do so in ways sensitive to what the agent (or better, I'll argue, the system) knows. F&S (sect. 5, para. 2–3) appeal to this possibility to “deflate” empirical evidence (such as Carrasco et al. 2004) suggesting that selective attention alters what we see even in cases where no overt action (such as head-turning or visual saccade) is involved. Selective attention, the authors concede, may indeed enhance specific aspects of the visual input. But such effects may be functionally similar to turning one's head, altering inputs that are then processed using a modular, inflexible system.
It is certainly conceivable that attention might always or mostly operate in just the blunt fashion that F&S suggest. But...