214 J.J.C. Smart
would infer a watchmaker. Watches do not grow spontaneously as heather,
kangaroos and snakes do. Behe argues in effect that on the contrary
heather, kangaroos and snakes do have a designer. However, though Behe
does touch on large-scale matters, such as that of the evolution of the eye, he
is mainly concerned with the amazing intricacies of biochemical processes in
the cell. Even to one unlikely to be budged from neo-Darwinism the book is
impressive in the detail it presents. Behe claims that the structures to which
he draws attention are ‘irreducibly complex’. A system is irreducibly complex
if taking away one component of it prevents it from functioning. He gives the
example of a mousetrap. It is irreducibly complex because if you take away
one component (e.g. the spring) it is useless for catching mice. He thinks that
many organelles in the cell are such systems. Functioning here is elucidated in
terms of fitness for survival of such species, but he is arguing for intelligent
design as an explanation. Design requires a designer and so he is arguing for
theism.
The example of the mousetrap may well illustrate the notion of irreducible
complexity, but Behe’s concern is to apply this notion to biology. A mouse-
trap contains very few parts and has no redundancy built into it. A better
analogy would be not to remove a component but to make very tiny changes
in the component itself, e.g. by changing its length imperceptibly. The mouse-
trap might then function but not quite so well. The usual reply to Behe is
that minute changes in suitable molecules due to happy changes in DNA may
lead to end results which may strike one as miraculous. For Haldane’s views
on Behe, see pp. 225 – 6. Of course many such changes will lead to unviability
or loss of functioning, but some will not – the complexity is not quite irreduc-
ible. The results may strike us as miraculous but seem so only because we are
not used to thinking in terms of time-spans of billions of years. Also we must
not forget how evolution by natural selection proceeds by successive steps (as
selection filters out possibilities) and so the improbability of the final result is
less than it would be if the whole thing had come about at once by chance.
Richard Dawkins, the leading popularizer of neo-Darwinism, is inclined to
define a miracle as a natural but improbable event. In the present philoso-
phical context it is more convenient to regard a miracle as a supernatural
event and then say that there aren’t any.
As against this, John Haldane in FE holds that the miraculous is needed to
explain evolution, but I would give the same answer as I have just done, thus
sticking with biological orthodoxy. Various conjectures have been made as to
how life could have arisen. Life gets going when a replicator, DNA or RNA
or some possible precursor of them that replicates, arises out of ordinary
chemical processes. Dawkins suggested one conjecture, the primeval soup
theory, in his book The Selfish Gene,^25 and plays around with another, due to
A.G. Cairns-Smith, where at first the self-replicating processes were silicon