10 J.J.C. Smart
physics needs to postulate them we must regard them as physical. Similarly
Quine has held that we should believe in mathematical objects, for example,
numbers and sets of them, because mathematics is part of physical theory
as a whole, and the theories are tested holistically by observation and experi-
ment. If Quine is right we must regard the mathematical objects as physical,
and yet they are not material. Thus I prefer to describe myself as a physicalist
rather than as a materialist, except in the context of the philosophy of mind
where I hold that the distinction is not important. A neuron or even a protein
molecule is a macroscopic object by quantum mechanical standards. The
theory of electrochemical nerve conduction, the operation of neurons, nerve
nets, and so on, is hardly likely to be affected by quantum field theory and
the like.^10 I concede that quantum mechanical effects can occur in the
neurophysiological domain: thus the retina is sensitive to the absorption of
a single photon. This need not be of any significant importance for under-
standing the general working of the brain.
As a corrective to the presently canvassed idea that the so-called ‘New
Physics’ is more compatible with religious views than was the deterministic
nineteenth-century physics of Newtonian particles and gravitational attrac-
tions, together with some ideas about electromagnetism and thermody-
namics, let us compare the present situation with that of the middle and late
nineteenth century when William Thomson (Lord Kelvin) questioned the
estimates that geologists had made of the antiquity of the earth. Kelvin had
several arguments, of which the most persuasive were (1) the rate of cooling
of the sun, assuming that the only source of its radiant energy was due to the
loss of potential energy in its gravitational collapse, and (2) calculations based
on the rate of cooling of the earth and plausible assumptions about the initial
temperatures inside the earth. Geology and evolutionary biology seemed
incompatible with physical laws, since Kelvin’s calculations allowed only an
age of 50 or 100 million years at most. The situation was saved in Kelvin’s old
age by the discovery of radioactivity. This suggested that there were other
possible sources of energy, even though the theory of nuclear fusion and of
the reactions that keep the sun going still lay in the future.^11 In any case
Kelvin thought that it was unbelievable that the emergence of life could be
accounted for on the basis of physical law. Though he was not a vitalist in the
crude sense, since he denied the existence of a specific vital energy, he seems
to have thought that though living beings obeyed the principle of conserva-
tion of energy, a vital principle enabled them to get round the second law
of thermodynamics which had been propounded years before by Kelvin
himself.^12
Contrast modern biology, with its strong biophysical and biochemical core,
its neo-Mendelian and neo-Darwinian theory of evolution, and molecular
biology in genetics. It is true that it is not known how life arose naturally