One of the most serious charges laid against atheism is that it is responsible for some of the worst horrors of the twentieth century, including the Nazi concentration camps and Stalin's gulags. The godless regimes of fascism and communism could only commit such atrocities because they were godless. How should atheists respond to this charge? Consider fascism first. In Spain, the Catholic Church was on the side of the fascist Franco in the civil war and continued to support him for many years after he came to power. Serious dissent of any kind did not emerger until the 1960s. Indeed, many saw the civil war as a kind of religious crusade against the godless republicans.

In Italy, the Vatican signed the notorious Lateran treaty with the fascist government in 1929, providing mutual recognition of fascist Italy and the Vatican State and making Mussolini the leader under whom Roman Catholicism became the official religion of Italy. Resistance to Mussolini grew throughout the thirties but at no time was there a clear majority in the Catholic Church opposed to his regime, even after 1938 when anti-Jewish laws were passed. So it is hard to see how atheism can be seen to be the driving force behind fascism in Spain and Italy.

The case of Nazi Germany is the most important one, but again in no way was Nazi Germany a straightforwardly atheist state. Hitler, for instance, maintained the traditional German view of women as needing to focus on "Kirche, Küche, Kinder" — Church, kitchen and children.

More substantively, a concordat was signed between the Nazi government and the Catholic Church in 1933, and the collusion between the Protestant churches and the Nazi regime was even closer. Resistance came not from the established Protestant churches but from the breakaway Confessional Church, led by pastors Martin Niemöller and Dietrich Bonhoeffer. These dissidents are justifiably held up by Christians today as shining examples of principled resistance to Nazism, but the fact that they had to leave the established church to lead this resistance is no cause for Christian celebration.

Also, complex though the causes of the Holocaust are, it seems impossible to deny the role played by religion in Christian anti-Semitism, which was at least partly to blame for creating the mindset within which the Holocaust could even be conceivable.

The idea that atheism was the driving force of European fascism does not therefore seem at all persuasive. Things are rather different when it comes to Soviet communism. Here there is no question that we had an avowedly and officially atheist state which under Stalin's rule in particular practised mass extermination on a horrific scale.

However, the fact that the Soviet Union was atheist is no more reason to think that atheism is necessarily evil than the fact that Hitler was a vegetarian is a reason to suppose that all vegetarians are Nazis. It is certainly an historical refutation of the idea that atheism must always be benign, but it is a very naïve atheist who thinks that it is impossible for atheists ever to do wrong. If the Soviet Union provides some kind of refutation of atheism, then atrocities such as the crusades or inquisitions would likewise refute Christianity.

If the history of the Soviet Union is to be used in a case against atheism, it therefore has to be shown that it was somehow an inevitable or logical consequence of atheist beliefs. This is simply not plausible. The mere existence of millions of humane atheists in Western democracies who have no truck with state communism shows that there is no essential link between atheism and the gulags.

In fact, even though it was officially atheist, it is not even true to say that the Soviet Union and the church always had an antagonistic relationship. Stalin permitted the formation of the Moscow Patriarchate, a central body for the Russian Orthodox Church. According to historian Michael Bordeaux, throughout the years of Soviet rule, the Patriarchate "overtly backed every military initiative of the Soviet regime".

The Soviet experience does however point to two dangers of atheism. The first of these is a too-zealous militancy. It is one thing to disagree with religion and quite another to think that the best way to counter it is by oppression and making atheism the official state credo. Atheism's model should not be Soviet-style state atheism but western-style state secularism, in which matters of religion and belief are not regulated by government but left to individual conscience, in line with the broadly liberal tradition of individual liberty.

The second danger Soviet communism warns us against is the belief that society can be ordered by rational principles without regard to its traditions and history or a respect for the liberty of the individual. It should be remembered that many western intellectuals, including atheist freethinkers like Bertrand Russell, were originally very optimistic about the Soviet revolution. There was a naïve belief that it was possible to wipe the slate of society clean and start again following only rational principles of what is fair, just and efficient.

It is not at all necessary for atheists to go along with this belief and indeed, hardly anyone now does. Nevertheless, there is still a danger of overestimating the extent to which things could be better if only we ordered society more rationally. Imposing a 'more rational system' on an unwilling populace, will result in catastrophe.

Adapted from Atheism: A Very Short Introduction, published by Oxford University Press