Those who support science generally agree that its purpose is to explain what we observe by developing a model (or picture) of an underlying reality, identifying its basic components, and codifying the laws that govern it.  More than one model might satisfy the fundamental requirement that its consequences conform to our actual observations. Disagreements arise, even among science's supporters, in regard to what criterion should be used for selecting the preferred model from among the known alternative models, all of which satisfy the requirement.  Why, for example, does science explain the motion of the moon and planets by using Newton's laws of gravity and motion — as updated by Einstein — rather than the older rules attributed to Ptolemy?
    One popular criterion has the strong support of such staunch defenders of science as Paul Kurtz (chairman of the Council for Secular Humanism and the Committee for the Scientific Investigation of Claims of the Paranormal) and Eugenie Scott (executive director of the National Center for Science Education, which works diligently to keep evolution in — and creationism out of — the public schools).  This criterion identifies science with naturalism:  A model of reality is scientifically acceptable only if it limits itself to natural concepts, which are taken to be those familiar from physics, in particular matter and energy — in contrast with supernatural notions, such as spirit and miracle.  Other words often used to convey much the same idea as natural are material, mechanistic, and physical.
    What can be said in support of this criterion?  First of all, it certainly is compatible with what scientists actually are seen to be doing today.  The naturalistic jargon appearing in scientific papers is indeed readily distinguishable from, for example, the more mystical terminology likely to be encountered in theological discourse.  So another thing to say in favor of the alternative is that it fairly clearly demarcates science from religion, giving to each its own sphere of influence.
     A refinement makes this even firmer.  Science is identified with methodological naturalism as opposed to philosophical naturalism.  The former implies that naturalism is essential only while applying the scientific method and need not be adopted as a pervasive system of personal belief.  It therefore makes it possible for religious believers to accept and practice science.  If, on the other hand, science were equated with philosophical naturalism — the view that the supernatural does not exist — then it would become scientism — the view that what is amenable to scientific investigation constitutes everything that there is.
    Nevertheless methodological naturalism is inappropriate as a basis for a definition of science, for reasons I next shall discuss.
March 17, 2008
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