In the early stages of the First World War, observed the poet C J Squire, there was no escaping God:

God heard the embattled nations sing and shout:

"Gott strafe England" - "God Save the King" -,

"God this" - "God that" - and "God the

other thing".

"My God," said God, "I've got my work

cut out."

By the 1990s the liberal, secular nations of the continent that fought that war no longer felt any need to call on God. There was a settled assumption that our civilisation had reached a plane higher than one constructed on the crude certainties of religion. Once communism had been defeated in Eastern Europe, the whole pantheon - Marx, Lenin and Stalin as well as the Judaeo-Christian deity - seemed no more than ghosts of the past, ever decreasing in influence until they would be remembered, like the Greek gods, only in legends and friezes.

In Britain, churches faced drastically declining numbers: an estimated one million people gave up regular attendance in the 1990s. The pronouncements of Cardinal Hume continued to be taken seriously, although that owed as much to the former abbot's evident gravitas as his official role. The same could not be said of his counterpart at Lambeth Palace, George Carey, whose orotund estuary English seemed to indicate a diminishment of his office sadly not matched by his waistline (the novelist A N Wilson used to refer to him cruelly, but not inaccurately, as "Mr Blobby"). When Francis Fukuyama's The End of History and the Last Man proclaimed the ultimate triumph of liberal democracy in 1992, that victory appeared to be over religion as well as political ideology.

Since then, the challenges to liberal secularism in Europe have been obvious. They are a resurgent Islam; and the effects on the EU of an eastern expansion that took in more overtly religious populations. There were rows over whether a reference to God should be included in the now-abandoned EU constitution or the 2007 celebrations of the 50th anniversary of the Treaty of Rome.

God is back. And this time He isn't the woolly deity of the dear old C of E, so gentlemanly an old cove that He didn't appear to object when hardly anyone turned up on Sundays, or if one of His bishops cast doubts on His miracles or His existence. This time He has the whiff of brimstone about Him. But the truth is that we'd never got rid of God in the first place.

"Without God," wrote Dostoevsky, "everything is permitted." Proponents of secular liberal democracy would vehemently disagree, pointing to the UN's Universal Declaration of Human Rights, the European Convention on Human Rights or the EU Charter of Fundamental Rights. We're very fond of talking about rights, and we are highly attached to them. But even when we are not using the term sloppily - unless it's enshrined in law, for instance, you no more have the "right" not to breathe in my second-hand smoke on the street than I have the "right" to your last Rolo - we are all too hazy about where they come from.

Thomas Jefferson wasn't. Men's "certain unalienable Rights", he wrote in the American Declaration of Independence, were "endowed by their Creator". When God is in the picture it may well be "self-evident" where natural rights, or the human rights we talk of today, originate. When He isn't, these rights have their very foundations removed. If they don't come from God, they must come from man; and that puts them on a very different footing.

This isn't a problem for everyone. Some are happy to think of rights as no more than human constructs, the scaffolding of law we build around implicit social contracts. Rights become meaningful only when they are legally recognised as such, and are therefore mutable and subjective. You may have the right not to be hanged for a sheep today, but you wouldn't have done several centuries ago and, if parliament so votes, you might not do tomorrow. Under this interpretation, you have to accept that other societies may decide upon other types of rights, even ones that you might consider barbaric.

Yet this is far too thin a gruel to sustain most of us. The powerful appeal of the UN Declaration rests not solely on the fact that the General Assembly voted to adopt it in 1948. Groups of men and women have, after all, cast their ballots in all sorts of ways since ancient times; on its own, the act is not sufficient to bear lasting moral weight. We invest such declarations and conventions with a far profounder authority than that provided by a momentary human agreement. At a more basic level, this authority informs our attitude towards the law. The punishment for stealing, for instance, is not just the jail sentence; it's also societal disapproval, the sense that the thief has done something deeply wrong.

Ask anyone where all this comes from with-out God, and there is no satisfying answer. Talk about human nature or "inherent" rights may seem to make passable sense, but on examination fails to rise above assertion, or "nonsense upon stilts", as Bentham called the idea of natural rights; neither does it explain how some societies could have such different notions of property that our concept of theft made no sense in theirs, or why others found headhunting and cannibalism perfectly acceptable pursuits.

We have forgotten that there are tablets of stone on which we in Europe can find the ob jective morality we now prize so dearly. These tablets aren't hovering in thin air or somehow sewn into the fabric of the universe. They belong to the millennia of Judaeo-Christian tradition of which our societies are the product.

Filling a God-shaped hole

We have forgotten, too, that this objective morality did not exist separately from God; He was its source. No act was wrong in itself, it was wrong because God said so. Buried within the mulch of generations of practice, assumption, agnosticism and unchallenged belief are the real roots of our deep-seated notions of right and wrong, of freedom, liberty and natural rights.

Fukuyama acknowledged the link when he wrote, soon after September 11, that "the universalism of democratic rights can be seen as a secular form of Christian universalism". We may think we have removed the projectionist, but the projection - and the strength of our faith in it - remains even if, without a firm guiding hand on the machine, the images have become blurred.

How else to explain the new religions that we have created for ourselves? A religion of science, whose priests make proclamations imbued with a certainty that their empirical branch of learning cannot justify; a religion of rights which, however much we may instinctively agree with it, has no more coherent proof than that it is "self-evident"; and now, perhaps, a religion of ecology whose ministers thunder as self-righteously as any 17th-century Puritan preacher.

This search for certainty is entirely akin to religious belief. Both are types of faith, and if only the latter actually acknowledges God, the former does Him the compliment of seeking to fill a God-shaped hole. And that, for many people who acknowledge that there is an ultimately unknowable mystery at the heart of our very existence, is exactly what God is. I'd say that, nearly a century on, He's still got His work cut out.

God and me

Tod Wodicka, novelist

What does "God" mean? We perceive such a minuscule sliver of existence, and always will, that it is easier to say what "God" isn't. I'd bet that He isn't a patriarchal desert lord demanding worship and dietary/sexual peculiarities. But that's just a hunch.

Has God ever spoken to you? Insofar as I open my eyes each morning, yes. Beyond that, not a peep.

Where would we be without God? If "God" is reality or existence in its many and multiple guises, I'd say we'd be nowhere.

Jonathan Dimbleby, broadcaster

What does "God" mean? God is an idea that has captured the minds of humanity.

Has God ever spoken to you? Not once, and I don't expect to receive that metaphysical thrill.

Where would we be without God? We would be no better and no worse. We would be where we are, but we would use a different language to explain that. The idea of God has been an inspiration and the source of wonder. It has also been the cause of miseries.

Ann Widdecombe, Conservative MP

What does "God" mean? He is the supreme ruler of the universe and the one who will judge us at the end of our lives.

Has God ever spoken to you? God speaks to us all in different ways - it's up to us whether we hear Him.

Where would we be without God? We wouldn't.

Peter Tatchell, human rights activist (below)

What does "God" mean? The idea is synonymous with irrationality, superstition, ignorance, and usually dogmatism, insecurity, authoritarianism, intolerance, self-loathing and injustice.

Has God ever spoken to you? No, and neither has Father Christmas nor the Tooth Fairy.

Where would we be without God? Much better off, with a more enlightened, just and humane world. Although some religious leaders, such as Martin Luther King and Archbishop Desmond Tutu, have been liberators of humanity, religion has been mostly an instrument of war, bigotry and oppression.