A staple of accommodationist dogma is the notion that science can’t test the supernatural.  This has not only been the basis of U.S. court decisions that ban teaching creationism or intelligent design in the public schools (Judge Jones, for instance, argued this in the Dover decision in 2005), but is the official policy of some American scientific organizations on the science-vs.-religion debate.

The booklet Science, Evolution, and Creationism from the National Academies Press, for instance, says this:

Because they are not a part of nature, supernatural entities cannot be investigated by science. In this sense, science and religion are separate and address aspects of human understanding in different ways. Attempts to pit science and religion against each other create controversy where none needs to exist.

The National Science Teachers Association asserts:

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. . . as noted in the National Science Education Standards, “Explanations on how the natural world changed based on myths, personal beliefs, religious values, mystical inspiration, superstition, or authority may be personally useful and socially relevant, but they are not scientific.”

A statement by the National Association of Biology Teachers:

Explanations employing nonnaturalistic or supernatural events, whether or not explicit reference is made to a supernatural being, are outside the realm of science and not part of a valid science curriculum. Evolutionary theory, indeed all of science, is necessarily silent on religion and neither refutes nor supports the existence of a deity or deities.

And Judge Jones wrote this in his decision on the Dover Trial:

…we find that while ID arguments may be true, a proposition on which the Court takes no position, ID is not science…ID violates the centuries-old ground rules of science by invoking and permitting supernatural causation…While supernatural explanations may be important and have merit, they are not part of science…This rigorous attachment to ‘natural’ explanations is an essential attribute to science bydefinition and by convention.

If you’ve frequented this site, you’ll know that I disagree with this stand. I adamantly maintain that science can indeed test the supernatural—at least those claims about the supernatural that involve its interaction with the real world.  Indeed, you’ll be familiar with several claims about the supernatural that have already been tested, and refuted : the Genesis story of creation, the story of Adam and Eve, a 6,000-year-old earth, and the efficacy of intercessory prayer, as well as paranormal phenomena like near-death experiences, telepathy, and precognition.  If you invoke a form of the supernatural that claims to have real-world consequences, then those consequences necessarily fall within the ambit of science.  This means that any type of theistic faith involves hypotheses that are “scientific”. Dawkins was right to call the existence of God a “scientific hypothesis.”

One can think of many other supernatural claims that still remain to be tested.  The idea that certain rituals by Native Americans can bring rain, for instance, could be easily tested with controlled experiments. Ditto for the notion that sending money to the American huckster evangelist Creflo Dollar will bring you prosperity via the grace of God.

I’ve just read a very nice paper on these issues by Yonatan Fishman in the journal Science and Education (2009, free download), which I recommend it to everyone interested in this question.  Its main points are these (I’ll use quotation marks when I’m quoting Fishman directly):

• Science doesn’t “prove” or “disprove” anything.  It simply renders hypotheses more or less plausible (I’d argue, though, that science’s ability to render ideas implausible comes very close to what we all think of as absolute disproof). As Fishman says:

“Indeed, in science no hypothesis, regardless of whether it concerns ‘natural’ or ‘supernatural’ phenomena, can be definitively proven or disproven. The ultimate aim of science is to explain the world by means of models that are more or less supported by the available evidence. As new evidence may arise that conflicts with our currently accepted models, no scientific hypothesis or theory can be proven with certainty or be immune from potential falsification. Scientific theories and hypotheses are defeasible. Nonetheless, a rough probability value, perhaps assessed via the Bayesian framework outlined above, can still be placed on a hypothesis, such that the hypothesis can be ‘proven’ or ‘disproven’ beyond a reasonable doubt (a familiar example being the innocence or guilt of a defendant in a court of law).”

• The boundary between the natural and supernatural is fluid, as phenomena previously seen as supernatural (like lightning) are brought by science into the bailiwick of the natural.  Indeed, as I (JAC) see it, one shouldn’t really make a firm distinction between natural and supernatural phenomena, but simply characterize them as “produced by natural processes” vs. those “produced by divine causes.”

• A Bayesian probability perspective on religious claims shows that they can be strengthened or weakened by science until they reach the status of scientific “proof” or “disproof” as outlined above. With respect to God and religion, Fishman says:

“It is important to note that in disconfirming the existence of an entity or phenomenon, the absence of evidence is evidence of absence only when there is a good reason to believe that the evidence would be present if the hypothesis is true, or conversely that the evidence would be absent if the hypothesis is false (see Oaksford and Hahn 2004). Thus, contrary evidence is constituted either by the lack of evidence that is expected to be observed if the hypothesis is true or by the presence of evidence that is not expected to be observed if the hypothesis is true.”

In other words, we can provisionally accept that there is no god because we don’t see the kind of evidence that we should see if god were present (answered prayers, confirmable miracles at Lourdes, and so on), and we see things that we don’t expect if there were a loving, omnipotent, and omniscient God (the most obvious, of course, is the presence of undeserved evil).

• Indeed, if miracles, answered prayers, and regrown limbs were seen, the faithful would trumpet this as evidence for God, and of course many believers are always looking (in vain) for such evidence, viz. the search for the remnants of Noah’s Ark, the supposed authenticity of the Shroud of Turin, the ludicrous attempts of creationists to verify that the Grand Canyon was caused by the flood.  In truth, believers want, need, and look for for evidence for their faith. But in the end, that evidence always comes down to a kind of “knowledge” that is neither confirmable nor convincing: revelation.

• This all means that, contrary to the National Academies of Science, Judge Jones, the National Center for Science Education, and the American Association for the Advancement of Science, the idea of God and the supernatural are scientific (i.e., empirically testable) hypotheses, at least in principle.  Science can—and repeatedly has—tested the supernatural.  Sure, one-off miracles in the past, like the resurrection of Jesus, can’t be tested directly, but we can assess them as more or less credible by applying Bayes’s theorem (indeed, that’s what Hume was really doing when he asked whether it is more likely that a miracle happened or that the person reporting one was mistaken, deluded, or lying).

• Claims about the supernatural should be prohibited from science classes not because they’re religious, but because science has “proven” them wrong. In that sense the U.S. courts are misguided in always relying on religion alone to prohibit the teaching of creationism in schools. (However, it is impermissible under our Constitution to bring religious ideas into the classroom, and perhaps it’s easier for judges to assess that than to judge the scientific validity of different forms of creationism.)  Fishman notes:

“. . . claims should not be excluded a priori from science education simply because they might be characterized as supernatural, paranormal, or religious. Rather, claims should be excluded from science education when the evidence does not support them, regardless of whether they are designated as ‘natural’ or ‘supernatural’.”

• Naturalism is not a presupposition of doing science, but a conclusion from doing science. That is, we learn about the natural world from assuming that divine intervention or influence does not occur, and that the “laws” of nature are all that exists. We do not learn anything about the universe from bringing in the added assumption of a god. In other words, naturalism wins because it works.

I could go on and on about all the great insights in this paper—it seems to leave almost nothing unsaid that’s relevant to the topic—but I do urge you to download it and read it for yourself. If you’re not into math, you can skip the stuff about Bayes’s theorem, since Fishman explains it perfectly well in words.  But I’ll close with Fishman’s analysis of why scientific organizations and accommodationists keep claiming, in the face of reason, that the supernatural isn’t testable:

While the position that science cannot evaluate supernatural or religious claims —and hence that there can be no conflict between science and religion—may satisfy political aims (for instance, ensuring continued support for science by religious taxpayers), it is disingenuous, having the appearance of a ploy designed to protect religion from critical examination. Moreover, such a view is antithetical to the spirit of open and unbiased scientific inquiry, whereby any phenomenon, regardless of whether it is designated ‘natural’ or ‘supernatural’, should be a legitimate subject for study and critical examination.

Amen, brother.  Fishman is right to call accommodationists making the science-can’t-test-the-supernatural claim “disingenuous,” for that is what they are.  They should, and do, know better.

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Fishman, Y. I. 2009. Can science test supernatural worldviews? Science and Education 18: 1573-1901.