A fallible mind
It seems like an obvious statement, but the mind is not a perfect system. It can and is fooled time and time again. Conmen, magicians, spiritualists, psychics, religious figures and followers, are but a few of the people who either knowingly or unwittingly exploit the fallibilities of their own mind and the minds of others in order to push their beliefs. The Incas used to sacrifice young women in order to appease the gods, a practice that has not quite gone away yet. It was only a few hundred years ago that witches were being tortured and killed because of a false belief. This is a Demon-Haunted World, where people jump to credulous explanations that we know thanks to empirical inquiry are false beliefs.
There are two types of errors in this respect, false positives and false negatives. A false positive is believing something that isn't - like mistaking a shadow for a murderer. A false negative is not believing something that is - like mistaking a murderer for a shadow. Consider these two scenarios, which of the following two is more likely to lead to your demise? Mistaking a shadow for a murderer is a much more preferable option than mistaking a murderer for a shadow. Michael Shermer explains this here.
The brain does not work with complete information, the sheer volume of information that would need to be processed is phenomenal. To illustrate this, try this site out. The eye refreshes many times a second, but you are not taking in a complete image of the world each time. To find meticulous details, it requires focus and effort. By all accounts, the brain works on heuristics - on pattern recognition. This process by all accounts is not perfect, to see a professional magician (ironically named as what they perform is not magic by any stretch of the imagination), the performance is filled with misdirections and other assorted tricks in order to fool the mind.
But not all is lost, for all the times it fails, it is important to remember the successes. We are agents operating in an ever-changing environment. Just think of the way you operate on a day to day basis. I'm able to navigate around my house, find food, go to work and back, interact with other people and the environment around me. A fallible system does not necessitate a useless system, and the pattern-recognition software that can fail also has many successes. If you want to see this in action, have a friend perform a blind experiment for you. Get him to have two steaks, one that he has left out at room temperature for a few days and one that he has kept in the refrigerator. I'm going to bet that you could tell which one was the off meat every single time.
Well, what we know is that the belief in question was produced by adaptive neurophysiology, neurophysiology that produces adaptive behavior. But as we've seen, that gives us no reason to think the belief true (and none to think it false). We must suppose, therefore, that the belief in question is about as likely to be false as to be true; the probability of any particular belief's being true is in the neighborhood of 1/2.This is really bad reasoning as I've argued before. I am currently drinking a beer. Is it 50/50 that I'm justified in thinking that this beer is in-fact beer? It could be that I'm drinking water and my brain is going haywire. But I would argue that it is more likely than not that I am drinking a beer, even if I cannot be certain about it. I can gauge this from the years I have had drinking beer and water and while it may be a false positive, the pattern recognition software is detecting a strong hops taste - something which is present in American-style pale ales and not at all present in water. And this is only looking at two cases, there's a infinitude of possible scenarios in which could be reality and me thinking it's beer could only be an illusion.
The fact is that I have better reason to trust that it is beer than it is not because of the pattern recognition software in my brain. And this software, like all other components of my body are an evolved product. I can confidently say this because of behaviour of other animals that we observe in nature. A chimpanzee will use a rock to smash open nuts, and to aid her in this endeavour she will employ the use of a tree root as a fulcrum to smash the nut. Her child will reach in and grab the food from the rock, realising what is edible and what is not. This is complex behaviour born out of higher thinking as opposed to being hard-wired.
Operating in an environment does require a brain that will produce behaviours that will allow for the survival of the species. We have a means of positive and negative reinforcement about whether a particular course of action leads to desirable or undesirable consequences.
Consider a frog sitting on a lily pad. A fly passes by; the frog flicks out its tongue to capture it. Perhaps the neurophysiology that causes it to do so, also causes beliefs. As far as survival and reproduction is concerned, it won't matter at all what these beliefs areThat's exactly right, it doesn't matter if you think that a computer runs on electromagnetic forces being applied through semi-conducting material that have been arranged in such a way as to produce logic gates or that you think there is magic smoke in the components that when fairies come through the wires will produce pornography on-screen, the computer will still work regardless. So why is an explanation involving electromagnetic force better than the magic smoke explanation?
To argue that understanding for survival and understanding for truth are two mutually exclusive endeavours is downright fallacious. Quite simply, we need to have at least someone a grasp on our environment in order to survive therein. Our ancestors when visiting a watering hole would have to be alert for lions. Now if they jump at the slightest sound, then they would never be able to get a drink and that would be detrimental for survival - so being somewhat sure that it is a predator is important. Likewise, ignoring all sounds would also be detrimental for survival. In this cut-throat environment, getting it right is important and this is the power of natural selection to explain adaptation in the environment. Quite simply, adaptation for survival does involve a large part of pragmatic understanding of the environment around us.
Knowing this gives us an advantage, we can apply the same tools that allow for these functionality and apply it to beliefs. By assessing what works and what doesn't, there is a better chance of carrying a true belief than having one born out of pure speculation. In my earlier linked post, I talked of gravity. Now we can see that objects fall to the ground when dropped, right now I'm resting that beer bottle on the table on the exclusive property that the beer won't fall to the ceiling. I can apply this same observation to my computer, to the textbook, and even to myself. I have validation that gravity works every second of every waking hour of my life. And in this, I would feel very confident of knowing that if I walk off the empire state building I would fall to my death, despite never having been on top of the empire state building or watching someone fall to their death.
This is the success of science, it is purely pragmatic - truth is derived from observations of what does work. So while this truth is tentative and prone to future revision, the demonstration of science follows on directly from the survival mechanisms that our pattern-recognising brain uses. I can be almost as certain that the earth orbits the sun as I can that I am drinking beer right now, just as a chimpanzee can be certain that nuts can be cracked using a rock. Science is derived from what works, and what works can be seen by what causes us to survive. Yes, this will still produce false positives and sometimes lead to the rejection of false negatives. But that hardly matters, science works.
Science: it works
If evolutionary naturalism is true, then the probability that our cognitive faculties are reliable is also very low. And that means that one who accepts evolutionary naturalism has a defeater for the belief that her cognitive faculties are reliable: a reason for giving up that belief, for rejecting it, for no longer holding it.Sitting in front of me is a device that can do more calculations per second than the entire human race combined. I say this often, but it needs to be emphasised. This is an achievement of naturalism - by seeking to understand how the world works, we have been able to use this knowledge to create practical outcomes. I recently flew to Europe, travelling around 15,000km each way - and did this in just a single day. We've been able to build machines that can fly around the world, and even fly to different worlds. Recently we put a rover on Mars that was able to send back data from hundreds of millions of kilometres away. Yet these pinnacles of human reasoning have come from a position of naturalism - the very thing Plantinga is arguing against.
The obvious conclusion, so it seems to me, is that evolutionary naturalism can't sensibly be accepted. The high priests of evolutionary naturalism loudly proclaim that Christian and even theistic belief is bankrupt and foolish. The fact, however, is that the shoe is on the other foot. It is evolutionary naturalism, not Christian belief, that can't rationally be accepted.The obvious error, so it seems to me, is that when you misapply chance and neglect that higher beliefs are a recent addition to brain development, it misses that having an understanding of the world around us has the capacity to understand. And by focusing on keeping assumptions to a minimum while grounding explanation on evidence, then it keeps the false positive beliefs to a minimum. The apologists for bronze age thinking proclaim the uncertainty of the human mind only when it suits them, ignoring that the same kind of reasoning has led to very different conclusions about the same token throughout the world. It is theism that has no claim to truth as it doesn't even try to ground itself in reality, ignoring the means by which evolution shaped our brains to think and reject that in favour of a false positive belief. By not even trying to engage in how our brains work, they stand little change of being correct, and until they do so, their beliefs cannot be rationally accepted.