One difficulty with equating science and methodological naturalism is that the latter's supposedly happy reconciliation of science and religion does not please everyone.  Objections come, not only from many non-believers, who prefer that naturalism be accepted philosophically rather than just methodologically, but also from some believers, who object to naturalism in any form.  The promoters of intelligent design, for example, think that invoking divine intervention to explain the origin of species should be regarded as entirely scientific.  They complain — and rightly so — that naturalism writes the rules of the game of science so as specifically to exclude their explanation, which is dismissed a priori without a hearing, simply because it makes use of ideas that do not appear on an "officially" approved list.  They frequently gain debating points by pointing out how unfair this is.
    So methodological naturalism presents science as being biased, indicating that it seeks, not the best of all possible explanations, but only the best within a preordained category of favored explanations.  Moreover, methodological naturalism is incomplete, because it does not provide a way to select the best among several competing natural explanations.  (Why are Newton and Einstein preferred over Ptolemy?)  However, all of this is just plain wrong:  The fact is that science strives to discover the very best explanation, natural or otherwise.  The criterion really has things backwards:  What currently is said to be natural is so designated largely because it is endorsed by science, rather than its being scientific because it is natural.
    Finally, methodological naturalism is belied by the history of science.  Scientists always have felt free to introduce new concepts that prove to be useful, such as entropy and curved space-time, and to discard old ones that have been found to be inadequate, such as caloric and the luminiferous ether.  These comings and goings of concepts may sometimes tend to get overlooked, because old names often are assigned to what really are new ideas.  Matter, for example, used to mean something made up of hard indestructible particles, but now it refers to conglomerates of curious quantum mechanical objects that act sometimes like waves and sometimes like particles and that are capable of disappearing entirely by converting themselves into energy.  So it really is missing the point to define science in terms of what happens to be its content today, there being no guarantee that this content will remain unchanged into the future.
    So what is needed in a definition for science is a criterion that measures the relative merits of all competing explanations by the degree to which they meet some ideal that can be expressed in a metaphysically neutral manner — that is, without reference to whatever concepts may appear in any of the explanations.  I next shall discuss such a definition.
March 31, 2008
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