Plantinga on the Theory of Evolution

This is the second in a series of posts discussing Alvin Plantinga’s Where the Conflict Really Lies.  The first post is here.

The first claim made by Plantinga is that science and theism are not incompatible.  He considers a number of specific areas of alleged conflict and shows that upon careful examination there is in fact no conflict.  The first specific area of alleged conflict that he considers is the Darwinian theory of evolution.

Some think that theism and the Darwinian theory of evolution are in conflict – that theism makes (or implies) claims that are denied by the Darwinian theory of evolution and vice versa.  If that is so, then theism and the Darwinian theory of evolution cannot both be true.  If theism is true, then the Darwinian theory of evolution is false, and if the Darwinian theory of evolution is true, then theism is false. Plantinga, however, argues that theism and the Darwinian theory of evolution are compatible – i.e., that it is logically possible that theism and the Darwinian theory of evolution are both true.

Plantinga distinguishes between several different claims commonly thought to be included within the theory of evolution.

(1) There is the claim that the earth is very old, perhaps some 4.5 billion years old: the ancient earth thesis, as we may call it. (2) There is the claim that life has progressed from relatively simple to relatively complex forms (though in terms of sheer bulk or weight the simple forms still vastly overshadow the complex; bacteria outweigh all other living creatures combined). In the beginning there was relatively simple unicellular life, perhaps of the sort represented by bacteria and blue-green algae, or perhaps still simpler unknown forms of life. (Although bacteria are simple compared to some other living beings, they are in fact enormously complex creatures.) Then more complex unicellular life, then relatively simple multi-cellular life such as seagoing worms, coral, and jellyfish, then fish, then amphibia, then reptiles, birds, mammals, and finally, as the current culmination of the whole process, human beings: the progress thesis, as we humans may like to call it (jellyfish might have a very different view as to where the whole process culminates). (3) There is the thesis of descent with modification: the enormous diversity of the contemporary living world has come about by way of offspring differing, ordinarily in small and subtle ways, from their parents.

Connected with the thesis of descent with modification is (4) the common ancestry thesis: that life originated at only one place on earth, all subsequent life being related by descent to those original living creatures – the claim that, as Gould puts it, there is a “tree of evolutionary descent linking all organisms by ties of genealogy.” According to the common ancestry thesis, we are all cousins of each other – and indeed all living things. Horses, bats, bacteria, oak trees, and even poison ivy – we are all cousins under the skin (rind). (5) There is the claim that there is a naturalistic mechanism driving this process of descent with modification: the most popular candidate is natural selection operating on random genetic mutation, although some other processes are also sometimes proposed. Since a similar proposal was characteristic of Darwin (“Natural selection,” he said, “has been the main but not exclusive means of modification”) call this thesis Darwinism.

Finally (although this thesis is not part of evolution strictly so-called), it is often assumed that (6) life itself developed from non-living matter without any special creative activity of God but just by virtue of processes described by the ordinary laws of physics and chemistry: call this the naturalistic origins thesis.

Plantinga takes the first four of these claims to make up the theory of evolution, and together with the fifth claim they make up the Darwinian theory of evolution.

Plantinga argues that despite common belief to the contrary there is no conflict between the Darwinian theory of evolution and theism.  Some – including many Christians and naturalists alike – have thought that there is such a conflict.  More specifically, the claim is that there is a conflict between the Darwinian theory of evolution and the Christian doctrine of creation.  Plantinga describes the Christian doctrine of creation as follows:

A more important source of conflict has to do with the Christian doctrine of creation, in particular the claim that God has created human beings in his image. This requires that God intended to create creatures of a certain kind – rational creatures with a moral sense and the capacity to know and love him – and then acted in such a way as to accomplish this intention.

The Christian doctrine of creation is said to conflict with the Darwinian theory of evolution because of the random nature of the genetic mutations upon which natural selection operates to drive the process of descent with modification forward.  That these genetic mutations are said to be random is thought to be incompatible with the idea that God has brought about this process intentionally according to a preconceived plan.

Plantinga argues, on the contrary, that the sense in which the genetic mutations are random is not incompatible with their being caused by God.  He argues:

You might wonder whether random genetic mutations could be caused by God: if these mutations are random, aren’t they just a matter of chance? But randomness, as construed by contemporary biologists, doesn’t have this implication. According to Ernest Mayer, the dean of post-WWII biology, “When it is said that mutation or variation is random, the statement simply means that there is no correlation between the production of new genotypes and the adaptational needs of the organism in a given environment.” Elliot Sober, one of the most respected contemporary philosophers of biology, puts the point a bit more carefully: “There is no physical mechanism (either inside the organisms or outside of them) that detects which mutation would be beneficial and causes those mutations to occur.” But their being random in that sense is clearly compatible with their being caused by God.

God can cause the right genetic mutations to occur at the right time to bring about his preconceived plan to bring into existence creatures of a certain kind.  The claim that the process of evolution is unguided is not compatible with the Christian doctrine of creation, but that claim is not part of the Darwinian theory of evolution.  It is a philosophical gloss added to the Darwinian theory of evolution, usually without any recognition that it is not strictly part of that theory at all.

It is important to see how limited this result is. Plantinga does not argue that the process of evolution is in fact guided by God’s plan.  Nor does he argue that the process could not possibly have been unguided.  Rather, he argues only that there is no contradiction in supposing that the process of evolution is guided by God. This result is nonetheless significant.  Some naturalists (i.e., atheists) have tried to argue for the falsity of the Christian doctrine of creation from the truth of the Darwinian theory of evolution as follows:

(1) If the Darwinian theory of evolution is true, then the Christian doctrine of creation is false.
(2) The Darwinian theory of evolution is true.
—————————————————————————————————–
(3) The Christian doctrine of creation is false.

Many Christian accept premise (1). They are forced, therefore, to attack premise (2) in order to reject the conclusion (3).  This has allowed naturalists to present a false dilemma: either we must reject the Christian doctrine of creation or the Darwinian theory of evolution as false.  And, in so far as Christians chose to reject the Darwinian theory of evolution as false rather than the Christian doctrine of creation, then they are anti-science, or at least on conflict with science.  If Plantinga is right, however, premise (1) is simply false, and the argument supplies no warrant for thinking that the conclusion (3) is true even if we do accept that premise (2) is true. There is no conflict.

Plantinga also discusses the question of whether we have any reason to believe that the process of evolution is unguided by God’s plan or that of anyone else. He argues that we have less reason than is commonly supposed to think that it is.  It turns out that all that can be said is that it is at least possible that the process of evolution is unguided.  Plantinga suggests that the process of evolution may be extraordinarily improbable on the supposition that it is unguided, so much so that we may find the supposition that it is guided by God’s plan more probable.  But it is unclear how he could calculate those probabilities.

It is unclear to me why Plantinga makes this argument.  What he has set out to do is to show that the Christian doctrine of creation and the Darwinian theory of evolution are not incompatible.  He simply does not need to go on to show that there are insufficient reasons for believing that the process of evolution is unguided.  That claim is not part of the Darwinian theory of evolution itself or of science more generally (according to Plantinga), and so its denial by a theists does not place the theist into conflict with science.  And, even if there are sufficient reasons to think that the process of evolution is unguided, given the restricted range of evidence permitted by methodological naturalism, that would not provide a good reason for believing that it is unguided provided there are other reasons and evidence outside the range permitted by methodological naturalism for thinking that the process of evolution is guided.

In any case, the Darwinian theory of evolution is not incompatible with theism generally, or the Christian doctrine of creation specifically. And, theists are not required to refute the Darwinian theory of evolution in order to maintain the Christian doctrine of creation, as is commonly supposed by Christians and naturalists (i.e., atheists) alike.

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