Alvin Plantinga's recently presented (via Maryann Spikes at Ichthus77) an explanation of his Evolutionary Argument Against Naturalism (EAAN). He's setting the record straight about what EAAN entails. I want to respond to Plantinga's presentation of EAAN (I'll ignore the details about the prior post to which Plantinga is responding.) I argue that EAAN is, at best, a straw man argument against an impoverished version of naturalism. At worst, it relies on a hidden premise which places an unacceptably high restriction on what is rationally acceptable.
Here's Plantinga presenting the argument:
The argument goes as follows. First, I’ll use ‘N’ to abbreviate ‘naturalism’, ‘R’ to abbreviate ‘our cognitive faculties are reliable with respect to metaphysical beliefs’ and ‘E’ to abbreviate ‘we and our faculties have come to be by way of the processes appealed to in contemporary evolutionary theory’). Then we can state the argument as follows:
P1 P(R/N&E) is low
i.e., the probability that our cognitive faculties are reliable when it comes to metaphysical beliefs given the conjunction of naturalism with evolution is low.
P2 One who sees that P1 is true and accepts N&E has an undefeated defeater for R.
P3 One who has an undefeated defeater for R has an undefeated defeater for any of her metaphysical beliefs.
P4 N&E is a metaphysical belief.
C One who sees that P1 is true and accepts N&E has an undefeated defeater for N&E and hence can’t rationally accept N&E.
Several aspects of this argument seem questionable to me. P1 and P4 are problematic, as I will explain shortly. First, I will draw attention to a third point: EAAN contains a hidden premise. The conclusion says something about what we can or cannot "rationally accept," even though this concept is not present in any of the premises. For the argument to be valid, then, there must be a hidden premise:
P5 It is not rationally acceptable to hold a metaphysical belief if one has an undefeated defeater for that belief.
Why doesn't Plantinga make this premise explicit? More importantly, should we accept this hidden premise?
Some years ago, Plantinga wrote (The Nature Of Necessity, 1974, p. 221): "Were we to believe only what is uncontested or for which there are incontestable arguments from uncontested premises, we should find ourselves with a pretty slim and pretty dull philosophy. Perhaps we should have Modus Ponens; certainly not much more. The policy of accepting only the incontestable promises security but little else." It seems that the Plantinga of 1974 was not inclined to accept P5.
It is not obvious that we should only accept philosophical views which are indefeasible. In fact, defeasibility is a widely acknowledged and accepted property in many philosophical areas. Why not metaphysics? Counter-arguments for sophisticated philosophical positions always remain, and reasons are always available for rejecting them. (Plausibly, any attempt to defeat such defeaters will only make room for their reinforcement.) Philosophy would amount to virtually nothing if we limited ourselves only to those views which permitted no defeaters. We must accept that which it makes sense to accept, even when reasons to reject it are inevitable. When deciding whether or not a philosophical view is sensible, it is not enough to show that the view in question permits a defeater.
Perhaps a more measured conclusion than Plantinga's would be warranted: It is not rationally acceptable to cling uncritically to a belief which permits of rational defeaters. I'll return to this point at the end of this entry.
I wonder if Plantinga has changed his mind since 1974. I admit I am somewhat ignorant of his output during the intervening years. Perhaps somewhere he has embraced P5. Regardless, I see no reason at all to accept it. Thus, my first reason for rejecting EAAN. We need a better reason to think that it is not rational to accept the conjunction of N and E.
Next, let's consider Plantinga's definition of "naturalism." Plantinga notes that his argument is only against his particular conception of naturalism. He writes: "In my argument I take naturalism to be the claim that there is no such person as God or anything like God—no angels, demons, or anything else supernatural." This presumes that the word "God" is coherently defined. It thus entails that theological noncognitivists cannot be naturalists.
I consider myself both a theological noncognitivist and a naturalist. My understanding of naturalism is a bit different. I understand it to be the view that there are no a priori limitations on scientific discoverability. Or, to put it another way, scientific methods can (in theory) discover all of the causes. (The fact that we call such discoveries "natural" is purely a political move, in my opinion.) My view does not stipulate any "natural realm" as opposed to some kind of "supernatural realm." I reject the idea that there is any theoretical space for the supernatural, but this is not obviously a positive metaphysical view. I thus consider myself a negative naturalist. My view might be characterized as methodological naturalism, since it does not clearly qualify as a metaphysical view. Plantinga's argument only applies to his version of naturalism, which must be taken as a positive metaphysical view. Thus, EAAN is of no apparent significance to me, other than a matter of philosophical curiosity.
This is particularly relevant when we consider the plausibility of P4. Is the conjunction of N and E a metaphysical belief? Evolutionary theory is a scientific theory, and it's hard to see why anyone would call it a metaphysical belief. Thus, if the conjunction of N and E is a metaphysical belief, the metaphysical stuff would have to come from N. Here Plantinga might be stacking the deck in his favor.
Plantinga has carefully selected the "naturalism" he is after: it is a positive claim about the non-existence of supernatural beings. Yet, what many naturalists are more likely to say is that they do not credit any claims about the existence of supernatural beings and that they do not believe in them. This is not necessarily a positive claim. The expressed lack of a certain sort of belief, and the rejection of claims of a certain sort, does not necessarily entail a positive view about the sorts of things in question. It might entail a strong skepticism about any and all positive views about the sorts of things in question. A person can reject all talk of the supernatural, and so self-label as a naturalist, without thereby adhering to a metaphysical view. They might verbalize the positive claim Plantinga uses to define "naturalism", but what they mean is that they do not believe in such things. The lack of belief is not itself a metaphysical view.
Plantinga might make the following counter-objection: Perhaps some kinds of naturalists are only of the negative sort, but surely there are positive ones out there. His argument is about the positive ones, not the negative ones. If that is the case, then it significantly limits the scope of his conclusion. Furthermore, I think negative naturalism is much stronger than positive naturalism. Thus, P4 is only true under a very limited, impoverished and not clearly representative conception of naturalism.
Finally, let's consider P1: It states that the conjunction of N & E makes the probability of the reliability of our cognitive faculties low when it comes to metaphysical beliefs. This could only be true if metaphysical beliefs aren't the sorts of beliefs that can be tracked by the sorts of tools which a blind process could select for. This would therefore discount any beliefs which were even indirectly relevant to survival and reproduction. Metaphysical beliefs, then, have to be fundamentally detached from what we might call the practical concerns of everyday life. Since there is no clear line of demarcation between such concerns and the more formal beliefs we develop through scientific methodologies, it is safe to say that P1 is only true if we take "metaphysical" belief to be in some fundamental way distinct from beliefs of any practical nature at all, including scientific as well as the more mundane sorts of beliefs which guide our lives.
Considering how useless metaphysical beliefs would have to be for P1 to be true, the obvious response is: So what? It's not at all clear that we should accept a view which takes such "metaphysical" beliefs seriously.
If EAAN leads us to any conclusion, perhaps it is this: The conjunction of N & E is not consistent with the uncritical acceptance of beliefs about matters which are of absolutely no consequence to our lives. We should be critical of positive (or "metaphysical") naturalism, though perhaps not quite as critical as we are about supernaturalism. Better would be to adopt negative naturalism, which is merely a rejection of beliefs about the supernatural. Negative naturalism, combined with evolutionary theory, is not a positive metaphysical belief at all, but a sophisticated skepticism combined with a scientific view of speciation. There is nothing obviously irrational about accepting that conjunction and believing that our cognitive faculties are not very reliable when it comes to so-called "metaphysical" beliefs. This is the sort of position most, if not all, naturalists would naturally accept.
Cosmetic adjustments made on Feb.26, 2012.