There was some interesting discussion over at Think Tonk recently. Clayton was arguing that theists can't fault Evolutionary Naturalism on the basis (advanced by Plantinga) that our rational faculties would be unreliable if EN were true. After all, such theists think we actually do have reliable faculties, and so if evolution created us just the way we are, then we would have the exact same (equally reliable) faculties. It's a neat - if flawed - argument, and provides a good opportunity to explore some modal issues that I'm interested in.
A key aspect of my response was to highlight two different ways of thinking about alternative possibilities. One is to treat them as standard counterfactuals, which involve presuppositions about what is actually the case. (For example, our judgment that if there was no H2O then there would be no water is based on the presupposition that the watery stuff of our actual acquaintence is H2O.) But there is another way to go, which is to conceive of the alternative as actual. (Call this conception "counter-actual".) For example, we might speculate about whether, perhaps, chemists are mistaken and water is actually composed of some other XYZ. Clearly our affirmation of the earlier counterfactual does not commit us to the absurd claim that if there is actually no H2O (because our watery stuff is really XYZ) then there is no water. Counterfactuals do not commit us to the corresponding counter-actuals.
This has important consequences for Plantinga's argument. Given the assumption that God created us with reliable faculties, the theist can't very well deny the counterfactual that if creatures evolved naturally to be just like we are, then they too would have reliable faculties. They must concede this much. But this doesn't entail the corresponding counter-actual. Plantinga can still consistently assert that if we actually evolved naturally, then we probably don't have reliable faculties. (I would dispute that claim, of course, but my point is simply that it is consistent with the aforementioned counterfactual.)
One way to understand this dialectic is to contrast the epistemic and metaphysical bases for the reliability of our faculties. Clayton points out that the reliability of our faculties supervenes on our constitution, and not its origins. So if we fix the constitution facts and let only the origins change, the 'reliability' facts will remain fixed. This is reflected in the counterfactual judgment.
However, suppose that our only reason for believing our faculties to be reliable is that we think God created us. Here it is facts about our origin, and not our constitution, that provide the epistemic basis for thinking our faculties to be reliable. So if we fix the constitution facts and let the origins change, then our beliefs about the 'reliability' facts should change. This is reflected in the counter-actual judgment.
These different judgments arise because counterfactuals map out a metaphysical modal space, whereas counter-actuals can instead be used to map out a sort of epistemic modal space.
I just thought that was an interesting point to clarify.
(Disclaimer: views and arguments attributed to 'Clayton' are presented here for dialectical purposes, and might not reflect Clayton's actual views. Readers are encouraged to read his blog for that.)