Professor Plantinga lecturing, 2009

Prof Alvin Plantinga, of Notre Dame University, is perhaps the most distinguished critic of current views on evolution. He claims that if our conceptual apparatus is simply the product of naturalistic Darwinian evolution, it will generally give rise to unreliable results. From this premise he argues that it is unreasonable to accept naturalistic evolution, since[1] if naturalistic evolution were true, our reasons for accepting it would be unreliable. There is nothing wrong with his logic, but his premise rests on a basic misunderstanding of how evolution works.

Disclosure: around the time of the Kitzmiller-Dover trial, Prof Plantinga and I had a long e-mail correspondence, now unfortunately lost during a University mail system upgrade. I remember, however, the final exchange. He said that Behe, Dembski, and Thaxton, advocates of three different versions of Intelligent Design, had produced arguments that required an answer. In reply, I said that I totally agreed; the answer was, in each case, that they were wrong. Prof Plantinga did not reply.

Disclaimer: I have no credentials when it comes to philosophy. But let me plead in mitigation that Prof Plantinga has no credentials when it comes to evolutionary biology.

According to Plantinga, a belief is warranted when it is produced by cognitive functions working properly, according to a design plan aimed at producing true beliefs. The design plan could be produced by an agent (God, or a super-scientist), or by evolution. This convoluted definition is necessary to bypass cases that puzzle philosophers, such as, is a belief warranted when it happens to be true but we hold it for bad reasons.[2] Plantinga’s position is encapsulated in the title of his 1993 book, Warrant and Proper Function.

I have three problems here. One is the choice of words; design plan and aim have connotations of foresightful agency, and it would be better to use neutral terms such as adaptationand tendency to produce. The second is circularity; how do we define proper function, if not in terms of giving warrant to beliefs when appropriate? The third, which is really a consequence of the second, is that it is useless in real disagreements, because it begs the question. For example, Prof Plantinga tells us that he possesses a sense of the divine, which he regards as a warrant. But how can he know that this is a warrant, unless he already knows that this sense is leading him towards the truth? And what, then, of Darwin’s objection (Part I); how can we have confidence in the beliefs that this sense induces, when those who claim to possess it differ so forcibly among themselves?

Plantinga is better when dealing with the limitations of our senses. He raises the interesting possibility that while they are not perfect, they are good enough, and that their deficiencies may represent a trade-off between speed and accuracy. This, I suggest, explains some shortcomings but not others. For example, in perspective illusions, such as the parked car illusion, we incorrectly perceive the image of the object further away from us as larger. This is a small price to pay for the ability to judge the real size of distant objects. There are other illusions, such as the disappearing dots, that have no obvious function, but are presumably byproducts of a generally efficient image processing system. There are, however, defects that can only be understood in terms of our evolutionary history. Thus, notoriously, the nerve connections to the mammalian retina run in front of the light-detecting cells, obscuring the view, and there is also a blind spot in each eye, where the optic nerve passes through the retina. If a freshman engineering student came up with such a design, we would gently suggest that he considered changing his major. After all, it doesn’t have to be like that; in the octopus eye, the parts are the right way round.

One of Plantinga’s examples inadvertently illustrates how evolution actually works. He considers[3] the case of an individual with extremely low blood pressure, and a fragile aorta. The low blood pressure restricts his physical activity, but if it rose to what is considered normal, his aorta would burst and kill him. So is the heart acting properly in keeping his blood pressure low? The answer would seem to be, yes, if and only if his design includes a mechanism by which a damaged aorta limits cardiac activity. (Much as our body temperature control system includes a mechanism that causes fever when we are fighting off disease.) For Plantinga, the heart/aorta example illustrates that we can only define proper function for an organ, including a human organ, in terms of a pre-ordained plan. On the contrary, I would claim, it illustrates the artificiality of imposing, on the complexity of biological forms, the simple criteria more appropriate to artefacts.

Now consider a primitive organism with very little in the way of blood vessels. Such an organism might have a very simple heart, encouraging circulation of fluid. There would be an adaptive advantage in channeling this blood flow, and once that happens, there would be further advantage in improving the performance of the heart. The heart and the circulatory system are under a selection pressure to improve, but only step by step. This is because there would be no advantage, and some cost, if one were to get too far ahead of the other. One can imagine further elaboration, if the creature develops separate organs for exchanging carbon dioxide in the blood for oxygen. Indeed, something like this seems to be what actually happened. A mutation in advance of the proper context would be lethal; a double-circulation heart could not function properly in a codfish. So if we are to apply the concept of proper function to organisms, it needs to be set in its evolutionary context (I do not expect Prof Plantinga to agree).

Throughout, Plantinga makes things far more difficult for himself by his rejection of the natural power of evolution. He makes heavy weather, as philosophers are bound to, of the “problem” of how we know that others have minds. As Plantinga reminds us, this is not a matter of ordinary logic or inference. After all, we are arguing from analogy with our experience of ourselves, i.e. from analogy with a single example. Indeed, unless we suffer from autism, we believe in other minds from the cradle, without arguing about it at all. So when Plantinga discusses how we come to have this belief, or why we should trust it, he can give no explanation other than Providence. However, we are social species, and both survival and mating opportunities depend on social competence. Thus there is strong evolutionary pressure to develop an adequate theory of other minds. There is good evidence that our brains contain “mirror neurons”, which respond to other people’s movements and gestures in the same way as to our own, bringing us as close as separate individuality allows to sharing other people’s sensations. But even without such knowledge of mechanism, we would be well aware, as philosophers have been since Aristotle, of the vital importance to each of us of insight into the minds of others.

The last chapter of the book is what drew it to my attention, with its claim that we cannot have warrant for believing in naturalistic evolution. For the most that naturalistic evolution could guarantee, is behaviour that increases fitness,[4] and Plantinga claims that there is no good reason to suppose that such behaviour requires true belief.

At this point, Plantinga commits a blatant act of distortion by quote mining, of the kind all too familiar to students of the creationist literature, but surprising in a scholar of his stature. He manages to invoke Darwin himself to support his position, with this excerpt from a letter to William Graham:

With me the horrid doubt always arises whether the convictions of man’s mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey’s mind, if there are any convictions in such a mind?

The quotation is genuine, but the meaning is completely distorted, by suppressing its context. Consider the passage in full:

Nevertheless you have expressed my inward conviction, though far more vividly and clearly than I could have done, that the Universe is not the result of chance. But then with me the horrid doubt always arises whether the convictions of man’s mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey’s mind, if there are any convictions in such a mind?

So the question is very narrow and specific; whether we can trust minds evolved from those of animals when they lead us to believe that the Universe had a creator. In Part I, I gave two other examples of Darwin showing similar reticence, because of how our minds evolved. But in both those cases, Darwin is addressing exactly the same question as here, which must have preoccupied him over many years. There is no honest way of recruiting Darwin to support the view that our evolved animal nature makes our minds unreliable on any lesser topic. Yet Plantinga manages to say (p 219[5]), almost immediately after his truncated quotation,

Darwin and Churchland seem to believe that (naturalistic) evolution gives one a reason to doubt that human cognitive faculties produce for the most part true beliefs: call this ‘Darwin’s Doubt’ (emphasis added)

The expression “Darwin’s Doubt” may well be familiar; Stephen Meyer chose those words as the title of his recent book in which he presents a long since deflated[6] perspective (see here and here and here and, if you have access to Science, here) on evolutionary change in the Cambrian.

But let that pass.

It is repeatedly clear that Plantinga understands nothing about how evolution works. For example (p 204) he imagines a sadistic dictator “inducing a mutation” into his enemies, which condemns them to a life of pain, and converts their visual fields to a shadowy green screen. He then asks, if possessing this mutation is made a condition for those enemies to breed, whether defective eyesight is now proper function. In reality, it is impossible to induce mutations in individuals who already exist, and the kind of change involved would in any case, even if possible, take many generations. Compare this “mutation” with the distortion actually induced in some pedigree dogs, which have been bred to have faces so flattened that they have difficulty breathing. But this took repeated selection, and close control of bloodlines. (And I would add that the conflict in both these cases between natural and artificial selection once again shows the problems of applying the concept of proper function to organisms.)

In a deservedly much-mocked passage (pp 225 ff), Plantinga tries to describe how a deeply mistaken worldview could still enhance fitness. For example, what if someone thought that it was delightful to be mauled by a tiger, and, at the same time, that the best way to ensure being mauled was to run away from it? Such a combination of beliefs would lead to survival-inducing behaviour, even though each of the beliefs was mistaken. But for this to happen without going through a lethal intermediate stage, each of the mistakes would have to occur in a single step, and both of them would have to happen at once; an unlikely coincidence of events improbable enough in themselves. If Plantinga doesn’t see the problem, I suspect that he has failed to appreciate the step-by-step nature of evolutionary change.

The evolutionary approach, incidentally, defines a role for pain, as Darwin realised (see Part I), and this role is, precisely, to induce correct beliefs about what is harmful. Plantinga’s account of beliefs does not require such preliminaries, and so the problem of suffering is much more acute for him than for a Darwinian.

Back to Darwin’s letter. When it comes to the mundane realities on which survival depends, there are indeed circumstances where we would “trust in the convictions of a monkey’s mind”. We know that monkeys are good at detecting predators, fear them, and signal that fear to each other. If we were in the jungle surrounded by monkeys, and they suddenly show signs of having detected danger, we would be foolish not to pay attention.

I have spoken of monkeys feeling fear. Yet a follower of Descartes would deny that animals have any feelings at all. How could I convince him? Perhaps by such evidence as the monkeys’ facial expressions and vocalisations, how these affect other monkeys, changes in activity in different regions of the brain, adrenaline release, blood flow, and skin temperature, all compared with the effects of fear in humans. Then what about less intelligent animals? Pursuing this route, we will soon find ourselves refining or breaking down the concept of “fear”, and embarking on a research programme, or indeed a family of research programmes, straddling the frontiers between ethology, evolutionary psychology, and philosophy. Such programmes are already well under way.

Our conceptual apparatus is indeed unreliable, but this is just what naturalistic evolution would lead us to expect. For the failings are most evident in areas where our errors would have inflicted the least damage on our fitness, and might indeed have enhanced it.

Such failings are numerous, and here are a few examples. Our common sense (or, as Bertrand Russell called it in Mysticism and Logic [free download here], our intuition) is most reliable on matters of immediate concern. Intuition tells me that I am sitting on a solid chair, in a room that is not moving, and only recently, in evolutionary terms, was it discovered that the chair is mainly empty space, and that the room that is moving eastward at several hundred miles an hour. I see patterns that are not there in reality; but better to see a tiger that isn’t there, hiding in the long grass, than to fail to see a tiger that is. As an infant, I understand physical events in terms of purpose and agency, rather than physical causation, and in some of us this tendency persists into adulthood. No surprise, since as an infant my very survival depends on interacting with other people, and getting them to care for me. I believe in the tribal gods, because this intellectual sacrifice qualifies me for membership of the group, with access to reciprocal altruism and reciprocal trust (see Jared Diamond’s The World Until Yesterday for more on that last theme). And those last few suggestions may or may not be true, but are at least credible, and suggest further research programmes of their own.

Given these failings, how, if at all, can our scientific beliefs be warranted? In 1520, science taught that the Earth was fixed, in 1820 that species were fixed, and in 1920 that the continents were fixed. Few people would now expect to see these views reinstated. So did they have warrant at the time? If they did, how much is a warrant worth? If not, how can we claim that our current beliefs are warranted? These are interesting and important questions, but not, I think, the questions that Prof Plantinga addresses.

Moreover, the problem of warrant is most acute in the very area where Prof Plantinga seems most certain of his own beliefs, namely religion. Here, all believers would claim warrant. But their beliefs are so diverse that, as a matter of arithmetic, most (if not all) of them must be mistaken. Yet here, surely, is the area where an Abrahamic God, desirous of being loved and worshipped, would have been most concerned to design us with access to sound knowledge of His reality.

It is not the naturalistic evolutionist who should be troubled by the problem of reliability, but the Intelligent Design creationist.

Photo by Jonathunder through http://en.wikipedia.org/wiki/File:AlvinPlantinga.JPG under the Creative Commons Attribution-Share Alike 3.0 Unported license. An earlier version of this post appeared here on 3 Quarks Daily

[1] He devotes some 20 closely argued pages to this logical step, but I think I have captured the drift. [2] If I understand him correctly, Plantinga would say that it is still warranted as long as we are in no position to realise that the reasons are bad. [3] I have changed the details slightly, in order to make the situation more plausible. [4] Plantinga generally refers to survival advantage, but fitness, the ability to survive and produce offspring that are themselves fit, is what actually matters. [5] Page number references are to Warrant and Proper Function, print edition, OUP 1993. [6] The “Cambrian explosion” isn’t what it used to be.