Evolutionary Argument Against Naturalism (p. 3)

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Evolutionary Argument Against Naturalism

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The ANPD Scenario

It would seem to be the case that Pr(R|N&E&SE) is low, but what if SE were false? What if in spite of Plantinga’s Argument Against Materialism, one is still convinced that the semantic content of a belief is causally relevant on naturalism? In that case there’s another thought experiment I’ll call the “ANPD scenario.”

Suppose a mad scientist creates an artificial neurophysiological device (ANPD), a many-tentacled device implanted near Smith’s brainstem that controls both his thoughts and behavior. The mad scientist can remotely control the ANPD’s electrochemical processes to vary Smith’s beliefs and behavior in innumerable and diverse ways. For example, Smith is dehydrated, and the mad scientist, wanting his victim to be in good health, uses the ANPD to force Smith to drink some water while simultaneously making him believe I am thirsty and this water will quench my thirst. The second time Smith is dehydrated, the mad scientist uses a different electrochemical setting to make Smith believe Drinking this water will grant me superpowers in the afterlife while producing the same drinking behavior (and suppose this belief is false). Here, the electrochemical process that produces fitness-enhancing behavior also produces a false belief. The ANPD can even produce “garbage” semantic beliefs that have little to do with the forced behavior, such as making Smith believe that Grass is air or that 1 + 1 = 3 at the same time it causes Smith to drink the water. The third time Smith is dehydrated the mad scientist configures the ANPD so that it causes Smith to drink the water while also causing him to believe Grass is air. Indeed, the mad scientist can associate just about any belief with the same drinking behavior.

For those who think that the semantic content just is neurophysiology and think that this avoids SE (it doesn’t, as I argue in the reductive and nonreductive materialism section in my article on Plantinga’s argument against materialism) let it be noted that the mad scientist can even use the device so that the physical properties of the belief Grass is air trigger an electrochemical reaction that causes Smith to drink the water, and this is possible because on naturalism it’s how a belief’s physical properties interact with the rest of the system that determines one’s behavior. So even if it were the semantic content of Grass is air that is causing the action here, the ANPD scenario would show that the semantic content need not cause behavior in a manner befitting a rational agent; the causal link could be akin to the effects of SE whereby the semantic content of the belief doesn’t even need to have anything to do with one’s external environment (thereby mimicking the effects of SE when SE says it’s the NP properties and not the semantic content that causes belief). To have some handy terminology, let’s say that semantic content is causally relevant in a meaningless way when it fits situations like the semantic content Grass is air causing one to drink water, and say that semantic content is causally relevant in a meaningful way the casual link is more apropos of a rational agent, such as when This water will quench my thirst is (part of) what causes me to drink water.

Such an artificial neurophysiological device is not only metaphysically possible, but it also seems to be physically possible (given that beliefs and behavior can be brought about by electrochemical means). The ANPD scenario shows that false beliefs can be associated with fitness-enhancing behavior, even to the point where the false beliefs are garbage beliefs (beliefs that are wildly unrelated to the external environment, as in dreams). But if the scenario’s artificial neurophysiology is physically possible, then it is at least metaphysically possible for an evolved creature’s natural neurophysiology to have the same “disconnect” between semantics and behavior. Even if were possible for a belief’s semantic content to be causally relevant, the ANPD scenario shows that for any given behavior B, there are innumerably many semantic contents C—even C’s wildly unrelated to the external environment—that could be associated with B. Like SE, this would still allow for the possibility for beliefs and behavior to be linked in a meaningful manner (e.g. I believe a plant is poisonous so I won’t eat it) but like SE, this also allows for the possibility of even garbage beliefs to be associated with advantageous behavior, and have belief/behavior disconnects identical in effect with SE even if SE were false, e.g. when the physical properties of Grass is air cause Smith to drink water, thereby mimicking the effects of SE when SE says it’s the NP properties and not the semantic content that is causally relevant. One could argue that the relation between semantic content and behavior is in this way functionally equivalent to SE in spite of the falsity of SE. Call this view semantic pseudo-epiphenomenalism (SPE).

Two key claims of SPE are (1) SE is false; (2) even though SE is false, it is still possible for even garbage beliefs to be associated with advantageous behavior (as by semantic content influencing behavior in a meaningless way)—and the ANPD scenario demonstrates that this is indeed physically possible (since the device is physically possible). The ANPD scenario thus shows that if SE isn’t true, then SPE is. Both SE and SPE permit a great divorce between beliefs and behavior (again think of the case where the belief Grass is air causes Smith to drink water). Upon reflection it’s very easy to envisage a set of moving atoms that create advantageous behavior while producing beliefs unrelated to the external world, and it’s easy to take for granted our rather fortunate truth-conducive relationship between belief and behavior because it is so familiar to us. Yet if naturalism were true and SE were false, semantic content being casually relevant in a meaningless way would be very possible.

To again avoid bias our own species, think not of us but of alien creatures on some other world where N&E&SPE holds for them. While it’s easy to assume that beliefs and behavior would be linked in a “rational” manner (e.g. a man believes water will quench his thirst so he drinks), there’s nothing on N&E&SE or N&E&SPE alone to believe such a link would occur for the aliens (whose physiology, we may presume, differs from ours), since both SE and SPE easily allow garbage beliefs to be connected with advantageous behavior. Because SPE is functionally equivalent to SE, and given the enormous variety of diverse beliefs that could be associated with a given behavior (e.g. Bachelors are married, Grass is air, 2 + 2 = 1, and 2 + 2 = 2) an evolving race of alien creatures afflicted with SPE has a low probability of evolving reliable cognitive faculties just as if they were afflicted with SE. In sum, naturalism entails that either SE or SPE is true, and since Pr(RA|N&E&SE) and Pr(RA|N&E&SPE) are low, it follows that Pr(RA|N&E) is likewise low. But then if Pr(RA|N&E) is low, then Pr(R|N&E) is also low (since, as with the case of the aliens, we are basically considering the likelihood of R on N&E without further relevant information).

A Rebuttal

In response one could put forth the following rebuttal. Even though naturalism unavoidably entails an SE-type problem—whether via semantic epiphenomenalism or semantic pseudo-epiphenomenalism—the fitness-enhancing neurophysiological properties that are most likely to be selected by natural selection (say that a certain neurophysiology is selectable if it’s likely to be selected by natural selection) happen to be those that are truth-conducive. The ANPD scenario, while physically possible, is contrived and produces certain belief-behavior pairs that are unlikely to obtain in real human physiology. The most selectable and efficient way for neurophysiology to produce advantageous behavior also produces mostly true beliefs. Thus, even though the SE-type situation exists for semantics and behavior, luckily for us the physiological relation between semantics and behavior is such that true beliefs usually obtain.

All that may be true, but as an objection against the Probability Thesis it falls short. A major problem is that even if a favorable physiological relation between beliefs and behavior obtains for our species, such a favorable relation does not appear to be knowable from N&E alone. It is not knowable from N&E&SE alone, nor is it knowable from N&E&SPE alone. To illustrate the problem, consider a planet with aliens whose neurophysiology radically differs from ours (though we don’t know much more about it). On N&E&SE where the semantic content of a belief is causally irrelevant, it would still be possible that mostly true beliefs are associated with advantageous behavior, but since the semantic content of their beliefs could be anything and it wouldn’t matter, it would be the most serendipitous of coincidences if that were to occur. Similarly on N&E&SPE where even garbage beliefs can be associated with advantageous behavior, it would still be possible that the alien electrochemical reactions causing advantageous behavior also generate mostly true beliefs, but it would be a rather serendipitous coincidence if that were to occur, given the enormous variety of beliefs that can be associated with a given behavior (as the ANPD scenario suggests) and given that we have no further relevant information about the physiology of the aliens.

One could concede that the probability of R given (just) N&E is low but also claim we know some proposition P (perhaps that the physiological relation between beliefs and behavior happens to be benevolent for our species) such that Pr(R|N&E&P) is high, and we have excellent reason to believe that P is true. Therefore, Pr(R|N&E) being low does not defeat R for the evolutionary naturalist. This however would be an objection against the Defeater Thesis rather than the Probability Thesis, so it will not be discussed in this section. Can the Defeater Thesis withstand this objection? For that matter, why accept the Defeater Thesis in the first place?

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[1] Plantinga, Alvin. “A New Argument against Materialism” Philosophia Christi 14.1 (Summer 2012) p. 21

Evolutionary Argument Against Naturalism (p. 2)

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Evolutionary Argument Against Naturalism

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The Probability Thesis

Why think Pr(R|N&E) is low? Ordinarily one might think that true beliefs help us survive. That certainly is the case if the content of our beliefs is causally relevant to behavior (e.g. I believe this plant is poisonous so I won’t eat it). But if the truth of our beliefs has no such causal relevance, then such a factor will be invisible to natural selection in the sense that while natural selection selects for adaptive physiologies and certain physiologies produce semantic content, which semantic content gets generated from a given physiology doesn’t affect natural selection’s outcome. So the content of our beliefs could be anything, true or not, and it wouldn’t affect our behavior. Whether the belief's content is 2 + 2 = 4, 2 + 2 = 67, or 2 + 2 = 4096 would make no difference to how we behave. If that is true, then Pr(R|N&E) is low.

The sort of naturalism being discussed here assumes that we human beings are purely physical creatures with no nonphysical minds or souls. In my article Plantinga’s Argument against Materialism I described Alvin Plantinga’s argument for the idea that if materialism with respect to human beings were true (i.e. if we were purely physical beings), the propositional content of our beliefs (e.g. There is a cold soda in the fridge) would not be causally relevant. For convenience, I’ll recapitulate some of that here.

To illustrate the idea of a belief’s semantic content being causally relevant to behavior, suppose I want a cold soda, and my roommate informs me that there is cold soda in the fridge. The belief There is a cold soda in the fridge is (part of) what causes me to go to the fridge and get a cold soda. We would naturally think it is by virtue of the belief’s content that this belief causes me to go over to the fridge. On dualism (the view that our minds are a composite of the physical brain and a nonphysical mental component, e.g. the soul) it is possible for a belief’s content to affect behavior; e.g. I believe something and on the basis of this belief my soul impacts my neural pathways in a certain way to cause behavior.

But on materialism, the coin of belief has two sides: the neurophysiological (NP) properties (certain neurons being connected in a certain way etc.) of the belief, and the actual semantic content of the belief (e.g. There is a cold soda in the fridge). If materialism were true, the content of a belief is causally irrelevant in the sense that (given materialism) a belief causes stuff by virtue of its NP properties, and not by virtue of its content. We can see this by doing a little thought experiment. Suppose a given person’s belief (a neural structure possessing semantic content), say, the belief that There is a cold soda in the fridge, had the same NP properties but an entirely different content—such as The moon is made of green cheese. Would the person’s behavior be any different if the belief had the same NP properties but different content? It would not, because having the same neurophysiological properties means we would have the same electrical impulses travelling down the same neural pathways and thus issuing the same muscular contractions. Thus if materialism were true, the content of our beliefs would be causally irrelevant. The view that a belief causes stuff by virtue of its NP properties and not its semantic content is called semantic epiphenomenalism (SE).

In response the critic of SE could say that there’s something wrong with the thought experiment because it is metaphysically impossible for a given set of neurophysiological properties to have a different semantic content. But even if it is impossible for a given set of NP properties to have a different semantic content associated with it, does this prevent the statement “If a belief had the same NP properties but different content, the same behavior would result” from being meaningfully true? I think not. In philosophy, statements of the form, “If P were true, then Q would be true” where P is an impossibility are called counterpossibles. It does seem that there are counterpossibles that are meaningfully true. For example, suppose renowned mathematician Kurt Gödel proved a certain theorem; it is impossible for theorems to be proved false since they are necessarily true. Yet as Alvin Plantinga points out, “If Mic were to prove Gödel wrong, mathematicians everywhere would be astonished; it is not true that if Mic were to prove Gödel wrong, mathematicians everywhere would yawn in boredom.”[1] So even if “If a belief had the same NP properties but different content, the same behavior would result” were a counterpossible, this doesn’t seem to prevent the statement from being meaningfully true.

More could be said about SE. If you’re still not convinced, I argue for it a little more in the reductive and nonreductive materialism section in my article on Plantinga’s argument against materialism (don’t worry, I explain what both sorts of materialism are!).

So why would it matter if N&E entails that the semantic content of our beliefs is causally irrelevant? To avoid bias against our own species, think not of us but of alien creatures whose physiology is radically unlike our own, and let RA represent the cognitive faculties of the aliens are reliable. N&E is true for these aliens, thus making the semantic content of their beliefs causally irrelevant. Then on N&E the electrochemical reactions that cause the behavior of these aliens could generate any semantic content at all (e.g. 2 + 2 = 1 or Grass is air) without that content affecting behavior. The semantic content could even be “garbage” beliefs unrelated to the external environment, as in dreams, and it still wouldn’t affect behavior. To illustrate the potential problem this creates, suppose a random belief is assigned for the answer to What does two plus two equal? Answers of one, two, rock, and sunshine would all be wrong. Randomly selected beliefs about the color of the sky and one’s age are similarly likely to be wrong. The enormous variety of “garbage” belief sets akin to dreams vastly outnumber those belief sets that accurately resemble one’s external reality. Since which belief set gets produced is invisible to natural selection, while it is still possible for the electrochemical reactions that produce advantageous behavior to also produce a reliably true belief set (as opposed to a garbage, dream-like one), it would be the most serendipitous of coincidences if that were to occur. Thus in the absence of further relevant information, the likelihood that their cognitive faculties are reliable (given N&E) is low, and thus Pr(RA|N&E) is low.

One could object saying that while the probability of cognitive reliability is low given just N&E, we know of further relevant information P such Pr(R|N&E&P) is high, e.g. we know that for own physiology, the link between content and behavior is favorable for our species, such that we act as if semantic content influences our behavior in a manner befitting a rational agent. Maybe that’s true, but that’s an objection to the Defeater Thesis and not the Probability Thesis. For now we’re just concerned with justifying Pr(R|N&E) being low. I’ve argued that Pr(RA|N&E) is true for the following argument:

1. If Pr(RA|N&E) is low, then Pr(R|N&E) is low.
2. Pr(RA|N&E) is low.
3. Therefore, Pr(R|N&E) is low.

I’ve already justified premise (2), explaining why semantic epiphenomenalism renders it unlikely that RA is true given N&E. What about premise (1)? What’s true for the aliens here is also true for us, since we are basically considering the probability of R on just N&E (we considered Pr(RA|N&E) merely so we could try thinking about the issue in a way that avoids bias towards our own species). But suppose that even after reading the rest of my article on Plantinga’s argument against materialism, one still isn’t convinced that naturalism entails SE. Is there another way to argue for the Probability Thesis?

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[1] Plantinga, Alvin. “A New Argument against Materialism” Philosophia Christi 14.1 (Summer 2012) p. 21

Evolutionary Argument Against Naturalism

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Evolutionary Argument Against Naturalism

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Some atheists claim there is a conflict between science and religion. But what if there were a conflict between naturalism (disbelief in the supernatural) and science? Enter the evolutionary argument against naturalism (EAAN), a remarkable argument that uses the theory of evolution to argue against the rationality of naturalism. This argument was originated by Christian philosopher Alvin Plantinga.

Overview of the Evolutionary Argument Against Naturalism

To define some terms and abbreviations, a defeater is (roughly) something that removes or weakens rational grounds for accepting some belief; in the context of the EAAN, the defeater is such that one is rationally obligated to withhold the defeated belief (i.e. not believe it; as by (1) remaining agnostic about it, or (2) believing it to be false). Suppose for example I arrive in a city and see what appears to be a barn from fifty meters away. I later learn that some eccentric has last week put up fake barns all over the area along with real ones, and that these fake barns are indistinguishable from real barns when viewed at a distance of thirty meters or more. I now have a defeater for my belief that I had seen a barn. I realize I could have seen a barn, but I don’t have sufficient grounds to accept the belief anymore. The rational thing for me to do is to withhold my belief that I had seen a barn. Suppose though I learn later that the eccentric removed all fake barns prior to my arrival. I would then have something that nullifies the defeating force of the defeater, i.e. a defeater-defeater.

Somewhat more precisely for the analytically inclined, in the context of the EAAN a defeater is a belief D that defeats another belief B for someone if that person would no longer be justified in believing B when coming to believe (and continuing to believe) D. So in our barn example (prior to learning that the eccentric removed the fake barns), the defeater D is “An eccentric put up fake barns in the area that are indistinguishable from real barns at the distance I was looking,” which defeats belief B “I saw a barn.” As long as I believe D, I cannot reasonably believe B with the information that I have. EAAN claims the naturalist who believes in evolution acquires a defeater for his belief in evolution + naturalism. The abbreviations commonly used for EAAN:

R =	One’s cognitive faculties are reliable
N =	naturalism is true
E =	evolution is true
Pr(R|N&E) =	the probability of R given N&E

In other words, Pr(R|N&E) refers to the probability that our cognitive faculties are reliable given naturalism and evolution, where by “cognitive faculties” the EAAN is referring to those faculties that process or produce beliefs—such as memory, perception, and reasoning. In a nutshell, the evolutionary argument against naturalism goes like this:

1. Pr(R|N&E) is low
2. The person who believes N&E (naturalism and evolution) and sees that Pr(R|N&E) is low has a defeater for R.
3. Anyone who has a defeater for R has a defeater for pretty much any other belief she has, including (if she believed it) N&E.
4. If one who accepts N&E gets a defeater for N&E in the manner described in lines (1) through (3), N&E is self-defeating and can’t be rationally accepted.
5. Conclusion: N&E can’t be rationally accepted (at least, not for the N&E believer who accepts premise (1)).[1]

Call premise (1) the Probability Thesis and premise (2) the Defeater Thesis. Denying the truth of evolution isn’t much of an option for the naturalist, so if the above evolutionary argument against naturalism is sound, the naturalist is in serious trouble. But defeaters can themselves be defeated as in the case of the barn scenario I described. Quoting Alvin Plantinga:

Of course defeaters can be themselves be defeated; so couldn’t you get a defeater for this defeater—a defeater-defeater? Maybe by doing some science—for example, determining by scientific means that her cognitive faculties are reliable? Couldn’t she go to the MIT cognitive-reliability laboratory for a check-up? Clearly that won’t help. Obviously that course would presuppose that her cognitive faculties are reliable; she’d be relying on the accuracy of her faculties in believing there is such a thing as MIT, that she has in fact consulted scientists, that they have given her a clean bill of cognitive health, and so on.[2]

Any would-be evidence or argument for one’s cognitive reliability would be relying on the very cognitive faculties that are being called into question, so the defeater mentioned in premise (2) would be an undefeated defeater.

Note also from Plantinga’s quote that we get a feel for what type of cognitive unreliability EAAN has in mind; this isn’t ordinary fallibility, the kind that we could compensate for by scientific methods and peer review, but a kind of general cognitive unreliability such that one can’t even trust one’s memory of whether one passed cognitive reliability tests.

So much then for an overview of the argument. Both the Probability Thesis and the Defeater Thesis of EAAN will need to be justified. Up next, justifying the Probability Thesis.

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[1] Plantinga, Alvin. Where the Conflict Really Lies (New York, New York: Oxford University Press, 2011), p. 344-345. Though I worded it slightly and I added the “pretty much” part to avoid possible controversies that things like cogito ergo sum and I am being appeared to redly might create, since by my lights the fact that there might be a few exceptions like this don’t affect the heart of the argument.

[2] Plantinga, Alvin. Where the Conflict Really Lies (New York, New York: Oxford University Press, 2011), p. 354