The first argument in favour of physical determinism is that from the success of science. Scientists have been singularly successful in explaining, predicting and controlling events in the last three hundred years, and it is claimed that it is a plausible extrapolation to suppose that they will go on being successful until they have explained all there is to explain. "But" as a leading physicist has cautioned, "one must beware of supposing that one can extrapolate indefinitely the range over which reasonably accurate predictions can be made. The original evidence for predictability was experimental; other experimental evidence can, and in company with most other physicists, I believe has, disproved such an indefinite extension." We may also, on a different tack, complain that scientists achieve their success in answering certain questions at the price of not addressing themselves to other questions. Many problems are ignored by the scientist on the score of their not being scientific problems. The canons of irrelevance are widely drawn. And therefore the success of science, although real, is limited.
The point is conceded, in practice, by most scientists. They admit that there are many questions they cannot answer, and that there are things they can learn from art criticism, moral philosophy, theology or politics. But the physicalist, who believes that everything can be explained in terms of physics, regards this as only a temporary imperfection. When all the laws of physics are known, and all predictions can be calculated, then all questions that can be properly asked will be answerable, and all that cannot be answered in his terms will be said to be unaskable, or mere coincidence. It is a Procrustean programme; but cannot be rejected simply because of that.
More telling still is the consideration that many forms of scientific explanation are not of the Hempelian form, of covering laws and initial conditions. Hardly any biological explanation is of this form, nor any geological one. Nor are most chemical ones, nor even many physical ones. Chemical explanations are very often time-independent. They show why some configuration is stable, rather than calculate how it changes with the passage of time. They are in terms of symmetries and group operators, not initial conditions and laws of development. So far as the practice of scientists go, there is little reason to fix on regularity explanation as the paradigm form of scientific explanation. Nevertheless the physicalist does so, and brushes off all other forms of scientific explanation as derivative and subsidiary. He does not disallow the questions from being asked, but is sure that he will have the answers, when his own physicalist scheme is complete.
Physical determinism is thus not a simple extrapolation from the success of science. It selects one pattern of scientific explanation in preference to others, not because the others have been found to be less sucessful in practice, but because the one is felt to be more explanatory in principle. There is a rational appeal about regularity explanation which makes us feel that it must be the paradigm of explanation, quite apart from any practical success it has had. Moreover, materialism has great metaphysical charm. We often feel that it must be true, not because it has been borne out by science but because it seems the only possible world view. Much of the pressure towards determinism is generated by a metaphysical materialism which we find compelling on its own account, quite apart from its determinist implications. In order to understand physical determinism we therefore need to appreciate the metaphysical pressures in favour of materialism.
J. R. Lucas
The Freedom of the Will
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