The Secular Outpost: The Problem with Metaphysical Naturalism (According to Victor Reppert)
First, I do share Parsons' concern about getting definitions right. When I deal with a naturalistic view, I offer an account of what that is supposed to have in it, which includes the mechanistic character of the base level, the causal closure of the base level, and the superveniece of everything else on the base level. By mechanism I mean that we are excluding from that base level four properties: intentionality, purpose, first-person subjectivity, and normativity. Now someone might come along and say that they have a view that doesn't fit these characteristics but is still naturalistic in some sense, in which case we'd have to look at their theory to see in what sense they're calling it naturalistic and whether I think a version of the AFR can be advanced against it. Here, I am going to assume that Parsons agrees with this account, and move forward.
Looking at this post, it seems to me that there are a couple of issues that we have to be careful about conflating. One of them is the claim that some version of nonreductive materialism can meet the argument from reason. In the combox, you get some discussion of that, and some responses to some exchanges with Clayton Littlejohn. However, the impression that I have had in discussion with Clayton is that he believes that mental events qua mental events do cause other mental states and physical states. Troubles with mental causation have been the focus of some of Jaegwon Kim's criticisms of nonreductive materialism, in particular the nonreductivism of Donald Davidson. Kim writes:
Davidson's anomalous monism fails to do full justice to psychophysical causation in which the mental qua mental has any real causal role to play. Consider Davidson's account: whether or not a given event has a mental description (optional reading: whether or not it has a mental characteristic) seems entirely irrelevant to what causal relations it enters into. Its causal powers are wholly determined by the physical description or characteristic that holds for it; for it is under its physical description that it may be subsumed under a causal law.
Jaegwon Kim, "Epiphenomenal and Supervenient Causation" ch. 6 of Supervenience and Mind, (Cambridge: Cambridge University Press, 1993) 106.
Now, of course, there can be a debate as to whether a case cam be made for mental causation in a non-reductive materialist framework. I think it can't. It's not that I don't think higher-level properties can be causally relevant. They can be if the are configurational combinations of physical states. If a bowling ball knocks all the pins down, this is perfectly possible even though basic physics makes no reference to bowling balls and pins. However, I take it if you add up the physical states and know what words mean, you can't avoid the conclusion that the bowling ball knocked down the pins. What I don't see is how you can add up non-normative states and get normative states, how you can add up non-intentional states and get intentional states, how you can add up non-first-person states and get first-person states, or how you can add up non-purposive states and get purposive states.
Science always prefers the most tractable accounts it can get. Scientists are happy when they can analyze the movement of a bullet through space, and determine what kind of impact it would have to make given the speed at which it was traveling. But there is another type of explanation that we might be interested in with respect to the bullet. It was fired by someone who had some intention with respect to what he wanted the bullet to do. Perhaps, he fired the bullet to kill his mother-in-law, whom he believes to be the worst person he knows. That is an agent-explanation, and as such is less tractable to science than a ballistic explanation. However, it isn't a total mystery; we can understand the person's motivations, and perhaps not find the action totally unexpected. After all, we are talking about the motivations of a fellow human. Now, as action might be the action of a superior being of some kind, and there it is even less tractable. Still, I would not want to call it a pseudo-explanation, because we can have some understanding of a superior mind, even the mind of God.
But it is a natural impulse in science to want to analyze the world in as tractable terms as possible, and hence we can understand why materialism is appealing from the point of view of science. However, at the same time, science described the activity of scientists in mentalistic terms. Scientists gather evidence, they form hypotheses, they perform logical and mathematical inferences, etc. It would indeed undermine the scientific enterprise if these mentalistic explanations of the behavior of scientists were simply untrue. Few people would be materialists if it weren't appealing from a scientific standpoint, but if mentalistic explanations are all false, then there are no scientists, and therefore no science. So, some kind of explanatory compatibility thesis must be defended by materialists. Scientists are, in the last analysis physical beings whose actions can be fully explained at the physical level as part of a closed mechanistic system, and their rationality, such as it is, must be some supervening property that emerges through evolution in a materialist world.
Parsons' strategy for establishing explanatory compatibility is essentially the same as the one Elizabeth Anscombe, (not a naturalist herself, but surely the most famous critic of C. S. Lewis's AFR). The mentalistic explanations we need in order for science to be science are compatible with materialism because those explanations aren't causal explanations, while those offered by physics are causal explanations.
Now Parsons, like Anscombe, points out that there are compatible explanations. Of course there are. For example, if we ask why the soda-can is sitting on the bookshelf, I might say "Because I put it there yesterday, since I am planning on recycling it," or "because it has a cylindrical shape, and is sitting on its base." But there are, certainly, incompatible explanations. Otherwise, there would be no hope that scientific explanations could ever supplant religious explanations.
Parsons tries to establish the explanatory compatibility as follows, using as an example Sam's acceptance of Krugman's arguments that the Ryan budget is a recipe for disaster.
When we say that Sam was convinced by Krugman’s arguments it seems to me perverse to attribute some very (I think in-principally) mysterious kind of causal power to the sense or propositional content of Krugman’s arguments. Attributing causal powers to Fregean Sinn (meaning), if this is what Victor wants to assert, just seems to me a straightforward category mistake. It is like saying that the set of all integers broke the deadlock between NFL players and owners. No, to say that Sam was convinced by Krugman’s arguments means that Sam considered Krugman’s claims, examined the supporting reasons, weighed them in the light of prior knowledge and norms of good reasoning, and judged that these were persuasive. However, considering Krugman’s claims, examining the supporting arguments, evaluating them, and judging them to be persuasive are things that Sam does with his brain, and happenings in Sam’s brain, being physical events, can cause things.
Well, if Sam's considering and accepting Krugman's arguments is a brain process, it looks like we are going to end up attributing properties to Sam's brain that are going to violate the causal closure of the physical. If Sam finds Krugman's arguments persuasive, one of the things he has to be persuaded by is the logical connection between the Krugman's premises and his conclusions. To be aware of something is to be causally influenced by it. So, yes, my awareness of a stop sign causes me to stop, not the stop sign itself. If I don't see the sign, I'll barrel right through. But, the stop sign has to cause my awareness of the stop sign. And if the physical is causally closed, then everything that I am aware of has to be also physical, and by physical I take it we mean that it has a particular location in space and time. A logical relationship has no particular location in space and time, and so if I am aware of a logical relationship, and that logical relationship affects my brain, then the causal closure of the physical has been violated, because something that has no particular location in space and time is bringing it about that I think certain things.
If I am aware that the cat is on the mat, then there is a causal connection between the cat and my brain, which occurs within space and time. If I am aware of the fact that, if a=b, and b=c and a=c, then in order for this awareness to be fitted within the framework of a causally closed physical order, that truth has to have a particular location in space and time. But it has not particular location in space and time, so, if the physical is closed, I can't be aware of it.
Explanations have ontological commitments. If I explain the existence of presents under the Christmas tree by saying that Santa put them there, then I commit myself to the existence of Santa. If I say I believe something because I perceive a logical relationship, that means that there are logical relationships. But where is this logical relationship for me to be aware of?
I don't see that you really resolve the problem naturalism has with rational inference by denying the causal character of these explanations.