If any one theory can be said to have converted the Western world to atheism, it is Charles Darwin’s theory of evolution.  The noted American sceptic Robert Ingersoll (1833-99) declared:-

This century will be called Darwin’s century.  He was one of the greatest men who ever touched the globe.  He has explained more of the phenomena of life that all of the religious teachers.  Write the name of Charles Darwin on the one hand and the name of every theologian who ever lived on the other, and from that name has come more light to the world than from all of those.  His doctrine of evolution, his doctrine of the survival of the fittest, his doctrine of the origin of species, has removed in every thinking mind the last vestige of orthodox Christianity.

But it is not at all clear that Darwinism does necessarily lead to atheism.  It is possible to conceive of a ‘God’ so remote from the affairs of this world that Darwin’s theory would have no bearing on his (or its) existence.  Aristotle and Plato may have believed in the existence of such a God.

The God with whom Darwin’s theory came into conflict was the God of natural theology as taught by men such as William Paley (1743-1805).  As an undergraduate, Darwin himself was impressed by the arguments of Paley.  These arguments were based on a succession of observations of living things that seemed to lead to the conclusion that all creatures were designed.  Paley famously drew an analogy with a watch: if we were to stumble upon a watch, would it not be obvious to us that it had not only been deliberately constructed, but designed with some particular purpose in mind?  And would we not infer from this the existence of an intelligent watchmaker?  Nature, Paley argued, is itself a mechanism, and so must have been intelligently designed.  Every living thing cries out: ‘We have been designed!  We have a purpose!’

One important weakness in Paley’s argument was that he assumed that God has created all living things in the present forms.  How could it be otherwise, since God had originally pronounced them ‘very good’?  Charles Kingsley was one who criticised this notion, insisting that God made things make themselves.

But it was Darwin who seemed to utterly undermine Paley’s thesis.  Paley’s account could not explain (a) why some species had died out, as the fossil record showed; (b) the peculiarities of island populations; (c) vestigial structures, such as the nipples of male mammals.  Darwin wrote in his autobiography,

The old argument of design in nature, as given by Paley, which formerly seemed to me so conclusive, fails, now that the law of natural selection has been discovered.  We can no longer argue that, for instance, the beautiful hinge of a bivalve shell must have been made by an intelligent being, like the hinge of a door by man.

Darwin’s theological views are sometimes described as ‘muddled’.  He wrote, ‘The mystery of the beginning of all things is insoluble to us; and I for one must be content to remain an Agnostic.’  But his reluctance to commit himself to thorough-going Christian theism had less to do with his views on evolution and more to do with his grief over the death of his daughter – which wrecked his belief in divine providence – and his distaste for the ‘damnable doctrine’ of eternal punishment of unbelievers.

But for Darwin there was certainly no Watchmaker.

In place of Paley’s carefully ordered natural world, in which each species was created already adapted to its unchanging environment, Darwin proposed a battlefield, in which emerging species fought for existence in a desperate struggle for survival.

Many thought that a synthesis was possible between Christian theology and Darwinism.  In 1884 Frederick Temple, later to become archbishop of Canterbury, argued that God did not merely make the world, but he made the world make itself:-

The scientific doctrine of Evolution, which at first seemed to take away the force of this argument [the argument from design], is found on examination to confirm it and expand it.  The doctrine of Evolution shows that with whatever design the world was formed, that design was entertained at the very beginning and impressed on every particle of created matter, and that the appearance of failure are not only to be accounted for by the limitation of our knowledge, but also by the fact that we are contemplating the work before it has been completed.

Charles Kingsley taught similarly, as did the American botanist Asa Gray.

It was not until the 1920 that, especially in NorthAmerica, a vocal minority of Christians began to insist that we must choose between Darwin and the Bible.  Things came to a head at the famous Scopes trial of 1925.  John Scopes was a biology teacher who had been accused of teaching evolution contrary to local law.  The defence was led by the celebrated agnostic Clarence Darrow.  Prohibited from using scientific testimony in his defence of Scopes, Darrow called prosecutor William Jennings Bryan to the witness stand.  Darrow was able to show that Bryan had no knowledge of geology, comparative religion, and ancient civilisations.  Although Bryan gained the legal victory, the judgment of history has been with Darrow.  Influential sceptics such as H.L. Mencken were able to portray those who opposed evolution on biblical grounds as intolerant, backward and ignorant.

The idea that evolutionary theory and theism are mutually exclusive was promoted by a number of writers in the second half of the 20th century.  Jacques Monod, in Chance and Necessity (1971) insisted that in molecular biology change arises by chance and is propagated by necessity.  It is impossible to speak of ‘purpose’ in the biological world.  We must come to terms with the realisation that our own existence is an accident:-

We would like to think ourselves necessary, inevitable, ordained from all eternity.  All religions, nearly all philosophies, and even a part of science testify to the unwearying, heroic effort of mankind desperately denying its own contingency.

Within a purposeless nature, we must create our own values and beliefs.  Nature offers nothing as a guide.

The ancient covenant is in pieces; man knows at last that he is alone in the universe’s unfeeling immensity, out of which he emerged only by chance.  His destiny is nowhere spelled out, nor is his duty.

Richard Dawkins, in The Blind Watchmaker, set out more popularly the implications of evolutionary theory.  He acknowledged that the complexity of living things gives the appearance of design and purpose.  But Paley could not have known what we now know, that what seems to be evidence of ‘contrivance’ is, in fact, the outcome of a long, blind, and purposeless evolutionary development.

Natural selection is the blind watchmaker, blind because it does not see ahead, does not plan consequences, has no purpose in view.  Yet the living results of natural selection overwhelmingly impress us with the appearance of design as if by a master watchmaker, impress us with the illusion of design and planning.

Design, then, is an illusion, and any theory of origins based on it must be abandoned.  But even if this is so, does it necessarily lead to atheism, as Dawkins has stridently asserted?

Stephen Jay Gould (1941-2002) has also popularised evolutionary theory.  He too had no place for design and purpose in an environment where everything can be explained in terms of natural selection.  But he insisted that

science simply cannot (by its legitimate methods) adjudicate the issue of God’s possible superintendence of nature.  We neither affirm nor deny it: we simply can’t comment on it as scientists.

Science can only work with naturalistic explanations.  Therefore, it can neither affirm nor deny the existence of God.

Empirically, as Gould observed, some scientists are theists and others are not.  Darwin himself was something of an agnostic, whereas the great American botanist Asa Gray (who advocated natural selection) was a devout Christian.  Charles D. Walcott, discover of the Burgess Shale fossils, was both a convinced Darwinist and a convinced Christian.  G.G. Simpson was a humanist agnostic.  Theodosius Dobzhansky was a believing Russian Orthodox.

Gould concludes:-

Either half my colleagues are enormously stupid, or else the science of Darwinism is fully compatible with conventional religious beliefs – and equally compatible with atheism.

Gould himself was an agnostic, inclining towards atheism.  But e maintained that Darwinists had no business pontificating on the existence and character of God.  The scientific data are ambiguous; other grounds must be found for denying or asserting theism.

Two major surveys of the religious beliefs of scientists, one at the beginning and the other at the end of the 20th century, showed remarkably similar results.  A survey in 1914 showed that about 40% of scientists had some form of personal religious beliefs.  When the survey was repeated in 1996, the result was just about the same.  (In the latter survey, a further 40% had no religious beliefs, and 20% were agnostic).

Based on McGrath, The Twilight of Atheism, 98-111.