The Gist Of It
Mathematically, Plantinga's argument looks like this P(R/N&E) where P is the probability of (R) the reliability of our beliefs, divided by (N) naturalism & (E) evolution. Plantinga's calculation of the P puts the probability of unguided evolution to favor true beliefs to be most likely very low. But why think it should be low?
It doesn't take an evolutionary biologist to see how under evolutionary theory, species that evolved sentience and could assess their environments would be favored for their survival advantage. And the more accurate the level of sentience, the greater the evolutionary advantage. There are two aspects to our beliefs. The first aspect are the cognitive faculties that we use to understand the world around us, such as our neurophysiology, sense of sight, hearing, and sense of touch etc. And the other aspect are our beliefs themselves that are dependent on the senses and the brain. Since it seems obvious that evolution would select for accurate senses, like for example the eagle's keen sense of sight, or the bear's keen sense of smell, then we have no reason to believe that the five senses humans have shouldn't accurately interpret the world around us. Our very evolution and survival depended on them being accurate for finding food and avoiding predators and danger.
This brings us now to our beliefs. Even though we may have evolved senses that are capable of accurately interpreting the world around us, that doesn't necessarily mean that every one of our beliefs are true. The truth is, our cognitive faculties aren't fully reliable, and that's exactly why we need science to help us determine what's real from what's imaginary. Recall the scenario in part 1 where I described the increased chance of the hominid's survival if it believed that a rustle in the bushes might be the result of a predator. Even though false positives are favored by evolution, once the rustle in the bushes can be investigated and it turns out to have been just the wind or a harmless animal, there's no logical reason to continue believing that it was a wild predator or the product of some unseen nefarious agent. Parallel this with the way our superstitious beliefs once made us inaccurately believe that naturally explained events in the world were caused by angry gods, and contrast that to how our modern scientific understanding of the world has shown us how the world really behaves. An investigation into the cause of the rustle in the bushes is in a way, tantamount to a modern scientific investigation into the true causes behind the beliefs that our senses hastily trigger.
Now that's the layman's argument.
Stephen Law's assessment of the EAAN exploits the assumption by Plantinga that the content of beliefs being true have no relation to adaptive behavior. "It can do its job of causing adaptive behaviour just as well if it is false as if it is true." Plantinga writes, "It might be true, and it might be false; it doesn’t matter." Law responds to this assumption:
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.
Law then jumps into an overly convoluted hypothetical involving probability of belief content and its correlation with adaptive behavior, but he concludes by saying:
Suppose that, solely in combination with a very strong desire for water, a certain belief/neural structure typically results in a subject walking five miles to the south. Surely, if there are such conceptual links between behaviour and content, then the property of causing that behaviour in that situation will be among those properties lending, as it were, a considerable number of points towards that belief/neural structure achieving the threshold for having the content that there’s water five miles south. Other things being equal, that belief/neural structure is much more likely to have the content that there’s water five miles south than it is, say, the content that there’s isn’t water five miles south, or that there’s water five miles north, or that there’s a mountain of dung five miles south, or that Paris is the capital of Bolivia. Perhaps the belief/neural structure in question might yet turn out to have one of these other contents. We can know a priori, solely on the basis of conceptual reflection, that, ceteris paribus, the fact that a belief/neural structure causes that behaviour in that situation significantly raises the probability that it has the content there’s water five miles south. Among the various candidates for being the semantic content of the belief/neural structure in question, the content that there’s water five miles south will rank fairly high on the list.
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.
He further adds:
If beliefs are neural structures, then it is at least partly by virtue of its having certain sorts of behavioural consequence that a given neural structure will have the content it does. If such constraints exist, then one cannot, as it were, plug any old belief content into any old neural structure, irrespective of that structure’s behavioural output.
What Law is basically saying is that there are conceptual links between a belief's content and that content's relationship with survival. If your very survival is on the line, you simply cannot entertain false beliefs without the ability to perceive true beliefs because false beliefs can be very costly in an evolutionary sense. So even though nature's tendency to favor false positives exists, it also awarded species accurate senses that can properly discern reality, and this can be used to investigate and falsify those false positives in particularly evolved species like us, in the form of what we call today science. But...even if there weren't any good explanations for why evolution would allow for accurate beliefs, the paltriness of the alternative hypothesis (that I critiqued in part 1) is bad enough when one considers the fact that it can only be justified with tremendous faith on supernatural events like original sin that stand in defiance (and in contradiction) of any serious scientific evidence. The alternative to naturalistic evolution is therefore an entirely faith-based position.
The very idea that evolution merely rewards adaptive behavior and not truthful beliefs actually would show why us religious beliefs are not true. But skepticism is actually not something very well rewarded by evolution, since we know it favors false positives over false negatives. So if Plantinga's account of naturalism is taken superficially, he successfully shows why religious belief isn't true, since that's what evolution would favor in the form of false positives. I think theists and naturalists alike can acknowledge the fact that humans have believed many far-fetched ideas that had little grounding in reality. It's safe to say that most of our beliefs throughout human history were false. The reason why this is so is clear: without science to test and falsify dubious beliefs, we had no way of knowing the truth except with what can be known a priori. Science has done a brilliant job at eradicating the nonsensical, and the triumph of naturalism over the past few hundred years is a testament to the power of science. To date, there isn't a single sufficiently explained phenomenon that has a supernatural cause. And the thing is, science can, in principle, verify the supernatural. All we would need to do is observe and measure a clear violation of the known laws of physics under highly controlled circumstances, in such a way where it would be obvious that intelligence was behind it. But I won't be holding my breath for the day when that happens.
Finally, Plantinga's own "sophisticated" theology itself has a built-in a defeater to his own argument that our beliefs are true because god guided evolution. When it comes to natural evils Plantinga says, "Satan and his minions, for example—may have been permitted to play a role in the evolution of life on earth, steering it in the direction of predation, waste and pain."* So if theistic evolution is true and if demons can tinker with the evolutionary process while god is powerless to stop them (in order to not violate their free will), then why should we believe our cognitive faculties and beliefs are accurate? Under Plantinga's sophisticated theological hypothesis, malicious demons could surreptitiously be playing tricks on our minds and they could've steered our evolution in such a way that made our beliefs untrue. And with this brilliant piece of theological insight, he destroys his own argument.
Plantinga is not offering a serious argument here if he actually expects the naturalist to entertain the idea that earthquakes, diseases and the evolutionary process itself can literally be caused or influenced by evil demons in order for his EAAN to be plausible. It's ideas like this that make me have to sigh in dismay at what happens when one rejects methodological naturalism in favor of supernatural conjecture. This is exactly why naturalism has been the preferred methodology of science since Darwin.
And lastly, if Plantinga represents one of the pinnacles of sophisticated contemporary theology, then his absurdities speak volumes about the intellectual bankruptcy of theology in general, and its failure to be congruous with actual science.
I am in the midst of developing a counter argument to Plantinga's EAAN. Mine is called the Evolutionary Argument Against God or EAAG, and it's designed to show how evolution is not compatible with the concept of an all-powerful, all-knowing and all-good god in the form of a syllogism. Stay tuned.
(Click here for the argument.)
* Plantinga, A, Where the Conflict Really Lies: Science, Religion, and Naturalism (2011, Oxford University Press). pp. 58-59