Science & Faith
8/6/13 at 10:23 PM 16 Comments

Darwin's Deeper Doubt Today: Theist Alvin Plantinga vs. Atheist Stephen Law

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Alvin Plantinga

Now that we have established Darwin’s own doubt about the reliability of evolved creatures to exercise certain higher order thinking skills, where is this conversation now? Do such deeper doubts about the capabilities of an evolved brain continue to undermine any good reason an evolutionary biologist might have to believe in his or her own theory today?

The most influential direction this conversation has taken in the last few decades centers on Alvin Plantinga’s Evolutionary Argument Against Naturalism (EAAN). You can listen to him make the argument here. I shall summarize the latest form of EAAN, which is how it is framed in his book Where the Conflict Really Lies: Science, Religion, and Naturalism (2011) and in this peer-reviewed journal article (the quotations below, if unidentified, come from this article).

For the sake of argument, Plantinga begins with the proposition that humans and all other life evolved by an unguided evolutionary process. If we begin with this assumption, and think carefully about both evolution (E) and naturalism (N), we find that N & E are incompatible. Because most naturalists today are also evolutionists, the incoherence of N + E is important to understand. How is holding to both N & E self-defeating?

Naturalism is the belief that “there is no such person as God or anything at all like God—or if there is, this being plays no causal role in the world's transactions.” When you put naturalism together with evolutionary biology, this would mean that all life evolved by an unguided process: natural selection acting on random variations. All that is selected for in this sort of evolutionary story is whatever manages to direct the body of an organism to survive and reproduce. In the case of complicated animals, this involves brain states that cause bodily motion.

Given evolution and naturalism, what could one say about the evolution of beliefs in the most sophisticated animals (or primitive human-like creatures)? Plantinga puts it this way:

A belief, presuming there are such things, will then be a physical structure of some sort, presumably a neurological structure. Such a structure, of course, will have neurophysiological properties (NP properties): the number of neurons and neural connections involved, the strength and rate of neuronal fire at different times and in various parts of the structure, the rate of change of strength and rate of fire in response to differential input, and the like. But it will also have a propositional content. It will be the belief that p for some proposition p: perhaps the belief that Marcel Proust is more subtle than Louis L'Amour. It is easy to see how beliefs thus considered can enter the causal chain leading to behavior; current science gives us a reasonably plausible account of the process whereby volleys of impulses propagated along the efferent nerves cause muscle contraction, motor output, and thus behavior. It is exceedingly difficult to see, however, how they can enter that chain by virtue of their content; a given belief, it seems, would have had the same causal impact on behavior if it had had the same NP properties, but different content.

He further argues that:

it will not be the case that a false belief causes maladaptive behavior by virtue of its having false content, and it will not be the case that a true belief causes adaptive behavior by virtue of having true content. The truth or falsehood of the belief will then be irrelevant to fitness and thus, so to speak, invisible to natural selection; but then it is hard to see how natural selection can promote or enhance or reward true belief (or reliable belief-producing processes) and penalize false belief (or unreliable belief-producing processes).

Plantinga (on p. 315 of Where the Conflict Really Lies) quotes atheist philosopher Patricia Churchland who also asserts that evolution is interested in adaptive behavior, not in true belief. He also cites several other non-theists including Charles Darwin and Friedrich Nietzsche who had similar intuitions about an evolved brain.

Let’s use an example that Plantinga has used on occasion. Many animals must run away from tigers in order to survive. Many false beliefs could have caused primitive humans to run from tigers, such as the belief that tigers are nice creatures we should like to pet and the best way to do that is to run away from tigers to trick them into letting us pet them. Even though this entails two false beliefs, it would promote survival among human-like creatures. So evolution favors only beliefs that lead to survival, and the number of possible false beliefs that promote survival is enormous compared to the few number of true beliefs that would promote survival in any given situation. So the odds are extremely low that evolution would produce fairly reliable minds, unless God guided evolution, which naturalists reject.

So if one believes in naturalism and the evolution of humans, then it is extremely unlikely that evolution produced the fairly reliable minds that humans seem to possess. This would also mean that this person who holds both N & E (in light of Plantinga's argument) would have no good reason to believe in evolution (E) or any other scientific theory. In short, believing in both evolution and naturalism is a self-defeating belief system.

Here is how atheist Thomas Nagel puts it (and I think he understates the problem a bit),

Evolutionary naturalism provides an account of our capacities that undermines their reliability, and in doing so undermines itself... I agree with Alvin Plantinga that...the application of evolutionary theory to the understanding of our own cognitive capacities should undermine, though it need not completely destroy, our confidence in them. Mechanisms of belief formation that have selective advantage in the everyday struggle for existence do not warrant our confidence in the construction of theoretical accounts of the world as a whole. I think the evolutionary hypothesis would imply that though our cognitive capacities could be reliable, we do not have the kind of reason to rely on them that we ordinarily take ourselves to have using in them directly--as we do in science. (Thomas Nagel, Mind and Cosmos, p. 27-28).

Atheist philosopher Stephen Law, in contrast to the largely EAAN-supportive Nagel, claims to have refuted Plantinga’s Evolutionary Argument Against Naturalism (EAAN) here.

Law’s own summary of his argument against Plantinga’s EEAN goes like this:

Here's the gist. Plantinga argues that if naturalism and evolution are true, then semantic epiphenomenalism is very probably true - that's to say, the content of our beliefs does not causally impinge on our behaviour. And if semantic properties such as having such-and-such content or being true cannot causally impinge on behaviour, then they cannot be selected for by unguided evolution. Plantinga's argument requires, crucially, that there be no conceptual links between belief content and behaviour of a sort that it's actually very plausible to suppose exist (note that to suppose there are such conceptual links is not necessarily to suppose that content can be exhaustively captured in terms of behaviour or functional role, etc. in the way logical behaviourists or functionalists suppose). It turns out that if such conceptual links exist, then (rather surprisingly!) natural selection will favour true belief even if belief content is epiphenomenal. So Plantinga is mistaken: even if belief content has no causal impact on behaviour, natural selection can still select for true belief. The EAAN is therefore refuted. To resurrect the EAAN, Plantinga would need to show that there are no conceptual links of the sort I envisage between content and behaviour, links of a sort that, as I say, do seem to exist.

Law brings into the conversation “certain further facts about belief “ that he thinks would allow natural selection to favor true belief. He writes:

Consider the suggestion that there exist certain conceptual constraints on what content a given belief can, or is likely to, have given its causal relationships to, among other things, behaviour. My claim is that, given the existence of certain conceptual constraints, unguided evolution will then tend to favour true belief.

Later Law writes:

But now notice that, given such conceptual constraints exist, unguided evolution will indeed favour true belief. Consider our thirsty human. He has a strong desire for water. He’ll survive only if he walks five miles south to where the only reachable water is located. He does so and survives. Suppose this adaptive behaviour is caused by a certain belief/neural structure. If there are conceptual constraints on belief content of the sort I envisage, and if a belief/neural structure in that situation typically causes subjects to walk five miles south, then it is quite likely to have the content that there’s water five miles south – a true belief. Were our thirsty human to head off north, on the other hand, as a result of his having a belief/neural structure that, in that situation, typically causes subjects to walk five miles north, then it’s rather more likely that the belief in question is that there’s water five miles north. That’s a false belief. Because it is false, our human will die.

After digesting Law’s arguments against Plantinga (you should read Law’s entire argument), here is why I think Law does not “defeat” EAAN as he claims:

  • Law seems to help himself to some generous assumptions about the existence and operation of survival enhancing “conceptual constraints” without offering a sufficient reason why they would likely exist and operate within an entirely materialistic (naturalistic) evolutionary process. He merely stipulates (postulates) them to exist to get his argument going. I suspect that he may be helping himself to some assumptions that are inconsistent with materialism, although I’m not prepared to articulate this now. I leave this as a project for others.
  • It seems, given evolution and naturalism, that the number of false beliefs that are survival enhancing would far out number the true beliefs that promote survival. Read again the paragraph above about a primitive human facing off a tiger and consider the huge number of possible survival enhancing false beliefs in this hypothetical evolutionary scenario (and others like it). Imagine a vast ocean of possiblity space representing survival enhancing false beliefs. Now picture widely separated tiny islands of survival enhancing true beliefs in that vast ocean. Get the picture? This suggests that evolution + naturalism gives us no good reason to trust what our minds/brains do. It seems that even Law's “conceptual constraints” cannot rescue us from this situation.
  • Law’s latest proposal is sure to stimulate another round of response and counter-response. I think it is too early to tell where this conversation will go next.

I will end this blog with a few of my own thoughts about the origin of complex forms of rationality, especially the kind that would be needed for the success of the natural sciences. Science-enabling rationality requires the freedom to think about alternative possible explanations to decide which best fits the evidence. But if chemical brain events determine human thoughts, then this sophisticated form of human rationality would not be possible. Physical stimulus and survival-enhancing response would rule the brain, which falls short of the sort of rationality needed for science. So, naturalism fails to explain the origin of scientific practice among humans.

Sophisticated rationality in humans requires a non-material rational soul. Although the mental and physical aspects of a human interact (it’s hard to think when you’re tired), they aren’t identical. This is a clue that unguided material processes alone cannot account for our origin. Indeed, Darwin never resolved his doubts about the ability of a haphazardly evolved brain to be rational. Despite impressive advances in neurobiology, we are no closer to a naturalistic account of rationality today.

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