Reality Conditions

Saturday, March 18, 2006

Are Evolution and Theism Compatible?

All over the Internet one can read discussions of this question, from the ludicrous creationist forums that provide material to FSTDT to scientific blogs like Pharyngula, and scholary papers on philosophy of religion. It was one of the latter that prompted me to write this post. But first, a bit of background.

Most sensible people, whether theists or atheists, appear to accept that the answer to the question is affirmative. It would seem that only religious fundamentalists that think that religion consists in taking the Bible as literal and complete truth, or fanatic atheists of the "Darwin disproves God" variety, would disagree with this. (The latter are much fewer and obscurer than the former, by the way; even arch-evolutionist and atheist Richard Dawkins doesn't claim this). But how is exactly the compatibility articulated? Usually one hears things such as "Evolution is the way God works", or "Evolution occurred in a way directed by God to his ends, including the appearance of human beings". The blanket term for this views is "theistic evolution", which seems to mean more or less "I have no quarrel at all with science, and just 'top it' with my claim that the process science describes is the way of God". Thus theistic evolution distinguishes itself from a view in which evolution happened but there were some miraculous steps in it that science cannot explain, as in some kinds of ID. But ID as a general "theory" is so vague that the term means little more than "I do have quarrel with the science of evolution: science is not enough, God is needed to explain evolution". Statements of ID and theistic evolution seem sometimes very similar, and the only difference is whether the speaker wants to "pick a fight" with science or not. This was highlighted last year when a Catholic cardinal found himself at odds with the "official" Vatican position on evolution, even though a very slight change of emphasis in his words could have made them orthodox.

But how exactly can evolution be "directed" by God in a way that does not conflict at all with science? According to science, there is a complete naturalistic story that provides an explanation for the emergence of present life forms, humans included. Doesn't this contradict the claim that the faithful would like to make, that the real explanation for our existence is the will of God? Such is the argument made by Alexander Pruss in this paper, which I found via the wonderful Philosophy Papers Blog (the closest thing philosophy has to an Arxiv).

I think his arguments are mistaken, and that the matter is of importance, because belief that religion and evolution are incompatible is the major force behind oppsition to evolution and by extension to science as a whole, mostly in America but increasingly also here in Britain. I think it is therefore important to articulate the consistency of science and religion in this particular. The position I'll be trying to defend is not my own, as I am not religious, but it is the kind of position I would hold if I believed in God and cared about not contradicting science, something I think is perfectly possible. (By the way, I know that one of the most notable Christian philosophers, Alvin Plantinga, defended arguments similar to Pruss's, but I couldn't spot the reference today).

What is Pruss's argument? He says that a naturalistic evolutionary explanation is statistical in nature, and that

Evolutionary explanations do not simply state initial conditions and give laws which together entail the obtaining of the explanandum. Rather, they sketch an evolutionary scenario that includes a number of mutation events as well as claims that these mutation events led to organisms with phenotypes such as to have promoted the passing on of the mutated genotypes. A crucial part of the story is that the mutation events are not predicted from the laws and initial conditions, but it is claimed that some set of mutations and environmental interactions that would lead to the occurrence of a species containing the "notable" features (under a sufficiently general description like "intelligence" or "acute vision") is not unlikely.
The “not unlikely” part is essential to the ambitious explanations that undercut Paley-style teleological arguments...

I agree with this as a good characterization of evolution as I understand it; call it E. Pruss goes on to consider four possible ways of reconciliating it with the theistic belief T that

God intentionally brought it about, immediately or mediately, that a human species exists, and did so in such a way that the design of that human species can be attributed to that intention, in the way that the design of an artifact can be attributed to the craftsman, to borrow the analogy in Isaiah 64:8 and Romans 9:21. This implies that the existence of a species having the mental and physical features of the human species is explained by God’s intentional activity.

I will discuss only the first of these ways, which assumes a deterministic universe. Of the other three, which assume an indeterministic universe, the most important is the second (which he calles Thomism) and his argument against it is a variation of that used against the first one. The third and fourth look like philosophical hair-splitting to my unsophisticated in theology eyes.

The first option, then, is that assuming the universe to be deterministic, God could have chosen the initial conditions to be such that eventually bring about the emergence of human beings as T requires, by the natural process described by E. The reason Pruss does not think this is a good reconciliation is that according to him the existence of a theistic explanation undercuts the naturalistic one. He says:

To see this, suppose that Fred has dropped, one by one, a thousand coins from a high building, and 485 of them landed heads. We may now wonder: “Why was the percentage that landed heads between 45% and 55%?” There is a simple statistical explanation here, it seems:

(1) The probability that between 450 and 550 of the coins would land heads-up is about 99.9%, and this is why somewhere between 45% and 55% of the coins landed heads.

But suppose now we learn a further fact. Fred had calculated at what angle and velocity he would have to drop every single coin in order that the coin should land heads and the angle and velocity needed for tails. Then he carefully chose the angles and velocities so as to guarantee that between 45% and 55% of the coins would land heads-up. I submit that this extra fact falsifies (1). It falsifies (1) not by falsifying
the probabilistic claim made, since that clam is nonetheless true.

What is now seen to be false is the claim that this probabilistic fact explains the result. For it no longer does. The reason is that the probability stated in (1) is no longer conditioned on the relevant background conditions, since now a part of the relevant background condition is that Fred tossed the coins in such a way as to ensure that between 45% and 55% of them would land heads-up. The conditional probability conditioned on this piece of background knowledge is 100%, not 99.9%, and it is this conditional probability that is explanatory of the result.

So Pruss's point is that if we are theists and accept T, we cannot go on saying that E is the explanation for our existence; the deep, true explanation is T. Is this argument sound?

Well, let's take a look at what it would imply. If the truth of the statement of evolutionary theory E was really incompatible with the deeper explanation T, then the theory of evolution would have indeed the logical consequence that God does not exist, or at least that He did not deliberately intend to create humans as T states. But evolution is a scientific theory and cannot imply these claims, which are purely metaphysical and beyond the realm of science. This should make us suspect that there is something wrong in the way Pruss understands the concept of "explanation" used in E.

To go further along this way, note that all statistical explanations in science would be in similar risk of being "undercut" in the same way as E, if Pruss were correct. Suppose we explain the existence of the rings of Saturn by saying that starting from a large planet and a large number of randomly moving rocks in the Solar System the final ring configuration is "not unlikely" according to Newtonian mechanics. This is a perfectly good scientific explanation, but for Pruss it cannot be the correct one because the particular ring configuration that we got is also a consequence of the initial condition of the universe, set by God. Of course Pruss may say that he knows by revelation that the initial condition was set specifically with the intention of creating humans, not planetary rings, so the intention of God is the "true, deep" explanation undercutting the naturalistic one for the humans and not for the rings. But (leaving aside the breathtaking anthropocentrism of this claim as something perhaps inevitable in traditional forms of religion) it sets the question of whether it is valid to distiguish, in the mind of an omniscient being that creates an entire universe with its laws, which things in the universe are "intended" and which are "byproducts". From my naive point of view this seems very presumptuous. The conclusion would be that those scientific theories that give statistical explanations for things "not intended by God" are sound and compatible with theism, while those that give them for things "intended" are not so, but how is the universe parceled between these two cathegories? It is not just a matter of a few "fancy" things like humans and planetary rings; the explanation of just about any macroscopical fact is satistical in nature. Pruss seems commited either to reject all statistical explanations in science, or to make an implausible distinction, among all created things, of those that were "intended" and those that were not.

The basic response to Pruss is that the E, and all other statistical scientific explanations, claim to be explanations only in a scientific sense, not in a trascendental sense. In the spirit of methodological naturalism presupposed by science, they claim to be the best explanations that we can give that contain only testable premisses and empirically accessible objects. When science says that the explanation for our existence is E, it is always assuming this sense of explanation. Thus when Pruss gives his recommended solution to the contradiction at the end of the article:

There is, however, an approach that only weakens evolutionary theory so slightly that it yields exactly the same empirical predictions as evolutionary theory does. To do this, we adopt the physically deterministic or Molinist solution, but drop the neo-Darwinian’s claim that the statistical facts are explanatory of the notable features of the human species. The argument against the physically deterministic and Molinist approaches is compatible with the truth of all the categorical and statistical claims of evolutionary theory, but was not compatible with the higher level claim that the statistical facts are explanatory of the features. This weaker version of evolutionary theory agrees perfectly with all the predictions of standard neo-Darwinian theory, and indeed with all first order claims about what mutations happened and when, what creatures reproduced and when, and so on. It is compatible with the existence of a chain of naturalistic causes leading from a unicellular common ancestor to the human species. It is simply incompatible with the claim that all of these facts provide a statistical explanation of various features such as intelligence in the human species. (...) Interestingly, if one holds that claims of explanation belong to a meta-theory rather than to a scientific theory on its own, then this view would allow one to say that the scientific theory of evolution is entirely true. However, I believe that explanatory claims are part and parcel of a theory.

he fails to see that the sense of "explanation" in which the explanatory claim is part of the theory is the scientific or methodologically naturalistic one, not the metaphysical one that conflicts with T. To highlight this the best metaphor (which I found first in Martin Gardner's wonderful The Whys of a Philosophical Scrivener, and attributed by him to C. S. Lewis and Miguel de Unamuno if I remember correctly) is that of the universe as a story written by God. Within the story, internal explanations of things that happen can be given from previous things that happened plus the "laws of nature" within the story and statistical principles; however, from a trascendental point of view the explanation for everything that happens in the story is the will of the Author. The analogy of Fred throwing coins to the street is not apt because in it Fred's will belongs to the natural chain of causation and can be used as a scientific explanation of the distribution of coins. A trascendental intention of God cannot be used in this way.

One reason Pruss might have gone wrong is that for atheists like Dawkins or Dennett (or myself) there is no trascendental level of explanation (or if we feel agnostic: if there is one we cannot know anything about it and therefore we better not take it into account). We hold that the scientific level of explanation is the best one possible. This is in itself not a scientific claim but a philosophical one (the difference between methodological naturalism and philosophical naturalism), but if one holds it then it follows that E is the explanation of our existence, period. But science per se is not commited to excluding a trascendental level of explanation, only to find the best naturalistic one. A theist is perfectly free to accept science as completely valid within its own realm. To say it more clearly: for the atheist (philosophical naturalist, "bright", whatever) the natural realm is the only one, so scientific explanations (that by essence are restricted to it) are the only ones and become explanations simpliciter; for the theist (or other kinds of metaphysicist) there is a trascendental realm, and if we have knowledge of it via reason or revelation we can use it to formulate trascendental explanations, but these are not in conflict with the scientific ones, as the story analogy should make clear.


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