May 27, 2010
Religion and evidence-7: Uniqueness and the problem of induction
(For the complete series of posts on religion and evidence, see here.)
In the previous post, I argued that under the rules of logic, existence claims placed the burden of proof on the person making the claim to provide evidence in support of it, while universal claims required the person disputing it to provide evidence. In the case of 'god exists', which is clearly an existence claim, the burden of proof is on the believer. Similarly the claim 'there is no god' is a universal claim and again the burden of proof (or disproof in this case) is on the believer.
It could be argued that the logic argument can be turned around, and that the statement that 'a natural explanation exists for this phenomenon' is an existence claim and that 'no natural explanation exists' is a universal claim, and so positive evidence has to be provided in support of the claim that an explanation exists. But as I said in the previous post, the symmetry is not exact. An existence claim for an entity (like an electron or god) is qualitatively different from the claim of existence for an explanation or theory.
But suppose for the sake of furthering the discussion that we ignore this difference and ask what evidence we can produce that a natural explanation exists for the alleged miracle. In the absence of producing an actual direct alternative explanation, the only evidence that can be supplied is historical, that it has been the case that event after event that were once thought to be inexplicable and thus miraculous have subsequently been found to have natural explanations. Furthermore, one never sees medical miracles in which (say) an amputated limb has grown back, which would really confound all expectations. All the medical miracle claims are of extremely subtle forms where the cures do not obviously violate any scientific laws and are not obviously incompatible with natural explanations.
Of course, all this historical evidence cannot prove that the current claim of a miracle is false because of the well-known problem of induction. The problem of induction says that there is no logical reason to think that just because some pattern of events has been invariably followed in the past, that the pattern will continue into the future. As an example, whenever I have let go of something in the past, it has always fallen down. Does that mean that the next time I let go of something it will certainly fall down? I may be fully convinced that it will, but there is no logical reason why it should, just as there is no logical reason as to why the Earth will continue to spin on its axis tomorrow.
The Vatican's chief medical expert was implicitly appealing to this when he said that, "the miracle is in the particular, in the exceptional; statistics cannot prove or disprove that singular cause-and-effect relationship." (Jacalyn Duffin, Medical Miracles (2009), p. 187). One of the features of scientific investigations is its repeatability and predictability. Miracles, by definition, are one-off events defying our expectations of regularity.
But of course none of us go around in a state of panic wondering if things will suddenly fall upwards or the Earth will stop spinning. The reason for our calm is that we use common-sense logical rules that enable us to arrive at conclusions that we are confident of even in the absence of proof. What we routinely do in such situations is to place the burden of proof on those claiming an exemption to the expected pattern to provide evidence as to why we should believe their claim. The reason we are amused by the iconic cartoon of a man carrying a sign "The world will end tomorrow" is because there is no reason to think that it will. Since the world has not ended so far, we feel safe in going to sleep tonight thinking that the sun will rise again in the morning.
In the case of medical miracles, what the weight of this historical evidence does is establish a prima facie case that since so many previous miracles have turned out to have had natural explanations, the latest miracle likely has a natural explanation too. To maintain that the latest case is an exception to this trend is to shift the burden of proof back to the people making the miraculous claim.
Science operates on the principle of methodological naturalism as described by George Gaylord Simpson (Tempo and Mode in Evolution (1944), p. 76):
The progress of knowledge rigidly requires that no non-physical postulate ever be admitted in connection with the study of physical phenomena. We do not know what is and what is not explicable in physical terms, and the researcher who is seeking explanations must seek physical explanations only.
Religious people may dislike methodological naturalism because it seems to shut out miracles but there is no denying that it has delivered the goods when it comes to advancing our knowledge. Abandoning it in order to allow us to say that inexplicable events are caused by god's intervention (which is really what miracles are claimed to be) is to risk losing a lot without gaining anything in return. By all means religious believers can choose to call inexplicable events acts of god. But it is perfectly reasonable and even desirable for scientists to reject such explanations if they are proffered without evidence in support of the existence of an agency that caused the event.
Philosopher David Hume in his essay On Miracles laid out a rule-of-thumb for determining how to judge whether an event is a miracle, saying "No testimony is sufficient to establish a miracle unless the testimony be of such a kind that its falsehood would be more miraculous than the fact which it endeavors to establish."
So applying Hume's rule, if one has a cure from an illness that is inexplicable on the basis of current knowledge, which would one consider to be more miraculous: the belief that god intervened, or its falsehood, that god did not intervene and there was a natural cause?
It seems to me that in the absence of evidence for the existence of some supernatural causation, it is perfectly rational and not at all unscientific to take the position that medical 'miracles' of the type described by Duffin are either the product of current deficiencies in knowledge or are improbable (but not impossible) events, and are not miracles in the religious sense in which the word is normally used.
POST SCRIPT: My article in The Chronicle of Higher Education
I was surprised to learn that my article The New War Between Science and Religion was the most viewed, emailed, and commented article. There were 170 (!) comments the last time I checked.
I received a nice little note of approval from Sir Harold Kroto, who shared the 1996 Nobel Prize winner in chemistry for his work on Fullerenes, which are molecules that consist of 60 atoms, all of them carbon, that are connected in a manner that in one form (commonly known as 'Buckyballs') looks like the geodesic domes constructed by the architect R. Buckminster Fuller. In following up, I found this excellent interview where Kroto talks about what motives we should have for doing something, competitiveness, science and the enlightenment, and the danger we face from irrational religious thinking by people who occupy important decision making positions.