Is naturalism coherent?

Here is how Huw Price characterises naturalism in a recent book, although I think it’s a characterisation that many philosophers would endorse:

What is philosophical naturalism?  Most fundamentally, presumably, it is the view that natural science properly constrains philosophy, in the following sense.  The concerns of the two disciplines are not simply disjointed, and science takes the lead where the two overlap.  At the very least, then, to be a philosophical naturalist is to believe that philosophy is not simply a different enterprise from science, and that philosophy should defer to science, where the concerns of the two disciplines coincide. [Expressivism, Pragmatism and Representationalism: 3]

But in what sense is it possible for philosophy to defer to science?  One way we might think this could go is in the following scenario: we have in our possession, say, both a successful scientific theory which posits backwards causation, and an a priori philosophical argument that backwards causation is impossible.  Deferring to science—which is an essential trait of naturalism, as understood above—involves accepting the scientific theory and rejecting the philosophical argument as (somehow) unsound.  But there is a problem with thinking of this as philosophical deference to science (as opposed to some other kind of deference to science).  Consider the maxim: When a claim of a successful scientific theory conflicts with the conclusion of an a priori argument, reject the conclusion of the a priori argument in favour of the claim of the successful scientific theory.  This is, on any reasonable measure, a philosophical dictum rather than the claim of a scientific theory.  In which case, someone who follows the maxim is being guided by a philosophical dictum rather than the claim of a scientific theory.  Moreover—although I’m not really arguing for this latter claim here—it is plausible that any adjudicative maxim of this kind would be philosophical rather than scientific per se; and in that case, it wouldn’t make sense to say that philosophy could defer to science.