Properly understood, secularism can be seen as Europe’s noblest achievement, the achievement which should be its primary contribution to the creation of a world order, while different religious beliefs continue to contend for followers. Secularism is Christianity’s greatest gift to the world, ideas and practices which have often been turned against ‘excesses’ of the Christian church itself.

What is the crux of secularism? It is that belief in an underlying or moral equality of humans implies that there is a sphere in which each should be free to make his or her own decisions, a sphere of conscience and free action. That belief is summarised in the central value of classical liberalism: the commitment to ‘equal liberty’ ...

This is also the central egalitarian moral insight of Christianity. It stands out from St Paul’s contrast between ‘Christian liberty’ and observance of the Jewish law. Enforced belief was, for Paul and many early Christians, a contradiction in terms. Strikingly, in its first centuries Christianity spread by persuasion, not by force of arms - a contrast to the early spread of Islam.

When placed against this background, secularism does not mean non-belief or indifference. It is not without moral content. Certainly secularism is not a neutral or ‘value-free’ framework, as the language of contemporary social scientists at times suggests. Rather, secularism identifies the conditions in which authentic beliefs should be formed and defended. It provides the gateway to beliefs properly so called, making it possible to distinguish inner conviction from mere external conformity.

Clearly there is much more to it than this, and as soon as we try and make laws about education or warfare or abortion or marriage, we find out what that “more to it” incorporates. But a striking argument, nonetheless.