Adventures in Branch-Cutting

Here’s a remarkable paragraph from Graham Oppy’s Atheism and Agnosticism, which appears in a discussion of whether theism or naturalism better explains our mental faculties:

Some – e.g. Plantinga (2012) and Reppert (2009) – argue that our reasoning capacities could not be a socially moulded mix of evolutionary adaptations and exaptations. But those arguments assume the reliability of our reasoning capacities in domains in which it is obvious that our reasoning capacities are highly unreliable: philosophy, religion, politics, and the like. When we make a more accurate assessment of the reliability of our reasoning capacities, we see that that assessment supports the claim that our reasoning capacities are a socially moulded mix of evolutionary adaptations and exaptations. (p. 42)

I had to read these sentences several times to confirm that Oppy really was saying what he seemed to be saying. Note two claims being made here:

  1. Plantinga and Reppert’s arguments assume that our reasoning capacities are reliable in the domain of philosophy (among other domains).
  2. That assumption is false.

In fact, Plantinga’s Evolutionary Argument Against Naturalism (EAAN) does not make that assumption, except in the trivial sense that EAAN is a philosophical argument and thus we have to assume that our capacity for philosophical reasoning is generally reliable if we’re to understand and evaluate the argument (in the same way that we have to assume the general reliability of our sense faculties when reading Plantinga’s books and articles). Plantinga’s argument is this: if naturalism is true, there’s no reason to think that our reasoning capacities are reliably truth-directed in any domain. (Actually, that’s a crude summary of a much more subtle argument, but it will do for now.)

The same goes for Reppert’s various versions of the Argument from Reason. In none of Plantinga and Reppert’s arguments does this unavoidable assumption — that our capacity for philosophical reasoning is generally reliable — feature as an assumption distinctive to the arguments themselves (i.e., in a way that doesn’t apply to philosophical arguments in general).

But the real surprise is that Oppy apparently rejects the assumption. He says it’s obvious (!) that our reasoning capacities are “highly unreliable” in the domain of philosophy. Yet he makes this claim as part of a philosophical rebuttal of Plantinga and Reppert, in the course of a philosophical case for naturalism, in a philosophical book written by a professional philosopher. If our reasoning capacities are highly unreliable in the domain of philosophy, what on earth does Oppy think he’s doing? This isn’t so much cutting the branch you’re sitting on as felling the tree and grinding the stump.

It’s so odd that I feel I must be missing something important.

Still, Oppy’s right about one thing: if our cognitive faculties are the product of undirected naturalistic evolution — which is to say, if evolutionary naturalism is true — then it’s highly unlikely that those faculties are reliable when it comes to philosophical matters. That’s a big problem for philosophical naturalists like Oppy.

All that said, Atheism and Agnosticism is still a useful primer on the subject.

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