by Paul Braterman
Science, some say, rejects supernatural explanations on principle; this is called intrinsic methodological naturalism (IMN). In Part I I argued, following the work of Boudry et al. (here, here , and here), that this strategy is misguided. Here I go into more detail, using actual past and present controversies to illustrate the point.
“I have no need of that hypothesis.” So, according to legend, said the great astronomer and mathematician Piere-Simon, marquis de Laplace, when asked by Napoleon why he had not mentioned God in his book. If so, Laplace was not referring to the hypothesis that God exists, but to the much more interesting hypothesis that He intervenes in the material world. And Laplace’s point was not, fundamentally, philosophical or theological, but scientific.
The planets do not move round the Sun in circular orbits, but in elliptical pathways, moving fastest when closest. All this and more Newton had explained using his laws of motion, combined with his inverse square law for gravitational attraction. There is one small problem, however. The planets are attracted, not only to the Sun, but to each other, perturbing each other’s pathways away from a perfect ellipse. These perturbations are not trivial, and in fact it was the perturbation of the orbit of Uranus that would lead to the discovery of Neptune. Newton himself surmised that they could, eventually, render the entire system unstable so that God would need, from time to time, to intervene and correct it. Laplace devoted much of his career to developing the mathematical tools for estimating the size of the perturbations, and concluded that the Solar System was in fact stable. So Newton’s hypothesis of divine intervention was redundant, and it was this hypothesis that Laplace was supposedly referring to.
There is an irony here. Laplace’s calculation that the solar system is stable is true only in the short term, (say a few tens or hundreds of millions of years). In the long enough term, the situation is much more uncertain. As Henri Poincaré was to show a century later, a system of three or more gravitationally interacting bodies is potentially chaotic. Under certain circumstances, an initially minute difference in starting conditions can lead to an ever increasing divergence of outcomes, so that eventually planets can adopt highly elongated orbits, or even be thrown out of their solar systems altogether. Modern computer simulations show (see here and here) that the solar system is indeed chaotic, that Mercury is vulnerable to extreme change or even ejection from the Solar System, and that it is possible that in some 3.5 billion years Mercury’s instability could be transferred to the other inner planets, including Earth, leading to the possibility of collision.
I don’t think that Laplace was claiming that God didn’t exist. It is just that He doesn’t intervene, to break the laws of Science. That must be the position of every scientist. A scientific law is not a scientific law if it only holds when some supernatural being decides to let things run, and not intervene.
A similar point of view had been put forward by Richard Lewontin, in his uncomfortably perceptive review, available here, of Sagan’s Demon Haunted World); I consider this review required reading for those defending science because of its all too rare recognition of creationism as a complex social problem:
Perhaps we ought to add to the menu of Saganic demonology, just after spoon-bending, ten-second seat-of-the-pants explanations of social realities.
I cannot do justice to Lewontin's reasoning by brief truncated quotations from his complex argument. It is clear, however, that he uses two very different arguments in rapid succession:
Nearly every present-day scientist would agree with Carl Sagan that our explanations of material phenomena exclude any role for supernatural demons, witches, and spirits of every kind, including any of the various gods from Adonai to Zeus…. We also exclude from our explanations little green men from Mars riding in spaceships, although they are supposed to be quite as corporeal as you and I, because the evidence is overwhelming that Mars hasn’t got any…
We take the side of science … because we have a prior commitment, a commitment to materialism. It is not that the methods and institutions of science somehow compel us to accept a material explanation of the phenomenal world, but, on the contrary, that we are forced by our a priori adherence to material causes to create an apparatus of investigation and a set of concepts that produce material explanations, no matter how counter-intuitive, no matter how mystifying to the uninitiated. Moreover, that materialism is absolute, for we cannot allow a Divine Foot in the door. … To appeal to an omnipotent deity is to allow that at any moment the regularities of nature may be ruptured, that miracles may happen.
The first paragraph is one that I can accept and advocate in its entirety. We reject supernatural causes in the same way that we reject implausible material explanations, because the evidence tells us that they don’t exist. The second, intertwined with observations that I have had to omit for brevity regarding the tenuousness of the pretensions of science and what he calls the patent absurdity of some of its constructs, is of a very different kind. Science, he says, is committed in principle to material causes, and the reason for doing so is, again, to exclude divine intervention.
Leave aside for now the problem of defining “materialism”; at a time when our concept of the material includes dark energy, particle entanglement, and quantum fluctuations in nothingness of which our entire Universe may be but one example, this is much the same as the problem of defining “naturalism” that I mentioned in Part I. Leave aside also the deliberately provocative antireligious language, inconvenient though that be for coalition builders. After all, Lewontin has, and is entitled to, his own agenda here. Leave aside even the possibility that miracles need not disrupt the normal business of science, as long as they are sufficiently rare. Hawking has followed Lewontin into the trap that awaits all those who would legislate the metaphysical out of existence. They lay themselves open to the charge that they are, themselves, arbitrarily introducing yet another metaphysical rule.
So, alas, does the National Science Teachers Association, whose commitment to IMN is quoted with approval by the National Academy of Sciences (Teaching About Evolution and the Nature of Science, 1998 but still current, and freely available here, p. 124):
Science is a method of explaining the natural world. It assumes the universe operates according to regularities and that through systematic investigation we can understand these regularities. The methodology of science emphasizes the logical testing of alternate explanations of natural phenomena against empirical data. Because science is limited to explaining the natural world by means of natural processes, it cannot use supernatural causation in its explanations. Similarly, science is precluded from making statements about supernatural forces because these are outside its provenance. Science has increased our knowledge because of this insistence on the search for natural causes. [Emphasis added]
This is very bad. We slide from an innocent-seeming description of the domain of science as the “natural” world, through the uncontroversial idea of testing explanations against each other, to the non sequitur of the sentence I have highlighted. There is an illusion of logic, based on an assumed dichotomy between the natural and the supernatural, but this is mere wordplay. We are given no other reason for this leap, even though it could have been justified, as Hawking and Lewontin justify their own exclusion of the supernatural, by reference to the assumption of regularity. As we saw in Part I, the claim that “science is precluded from making statements about supernatural forces” is simply untrue. Time and again, science has refuted the appeal to the supernatural by providing alternatives – if this is not “making statements about supernatural forces”, what is?
Present-day science does indeed make statements highly relevant to the existence or otherwise of supernatural forces. To raise the stakes to their utmost, some consider the Universe to be fine tuned for life, and regard this as scientific evidence for a purposeful Creator.