As well as the ripping up of a picture of Pope John Paul II on American TV, this journey has included being ordained as a priest and the release of a gorgeous reggae album, Throw Down Your Arms, in which she flirted with Rastafarianism. People have come to see O'Connor as slightly mad as a result, and I suppose they have a point, if by madness they mean a tendency to leave no thought, worry or question unexpressed or unexamined. But in her madness (I prefer eccentric curiosity) and the creativity that has flowed from that, she has given us some amazing and beautiful moments. I would go so far as to say that she is a national treasure.

Theology is a very nice . . . occasionally terrific . . . listen, although there is no question that some people are going to hate it.

Religion, God, biblical imagery are everywhere; and though it would be nice just to let the music wash over you, that is very difficult when the lyrics so insistently demand attention. But we are in the hands of a lovely singer here, a top class songwriter, a great band, and an experienced producer. In the end, listening to Theology is akin to being tickled vigorously by a very lovely nun.

Salman Rushdie is perhaps a mirror image of Sinead O'Connor, in the sense that much of his work . . . certainly the work for which he is best known . . . is contemptuous of religion.

In so far as Rushdie has ever had a spiritual quest, it ended with a teenage decision that religion was unnecessary and useless. "God, Satan, Paradise and Hell all vanished one day in my 15th year when I quite abruptly lost my faith, " Rushdie, born to a Muslim family, once said. "Afterwards, to prove my new-found atheism, I bought myself a rather tasteless ham sandwich, and so partook for the first time of the forbidden flesh of the swine. No thunderbolt arrived to strike me down. . . From that day to this I have thought of myself as a wholly secular person."

Last week, it was announced that Rushdie was to receive a knighthood from the Queen of England for his services to literature. The author . . . who has penned 13 novels . . . is one of the most decorated writers of the late 20th century. He won the Booker Prize in 1981 for Midnight's Children, which was also chosen in 1993 as the best Booker-winning novel of all time. The only surprise about his knighthood was that it had taken so long to arrive.

The reason for the delay, of course, was Muslim reaction to The Satanic Verses, Rushdie's 1988 novel which, according to its fundamentalist critics, mocked the prophet Mohamed.

Rushdie was sentenced to death under a so-called fatwa by Iran's Ayatollah Khomeini and spent many subsequent years under police protection.

It is at least arguable that the wishy washy response to the fatwa against Rushdie encouraged the hysterical and murderous reactions to perceived slights that have been so typical of the Muslim world in the last 20 years. The fuss over cartoons published in a Danish newspaper two years ago are one recent example of fundamentalist over-reaction; the response to Rushdie's knighthood is another.

Pakistan's religious affairs minister Mohammed Ijaz ul-Haq suggested last week that if somebody "exploded a bomb on his [Rushdie's] body, he would be right to do so unless the British government apologises and withdraws the 'Sir' title."

At a protest later that day, a student leader proposed that Rushdie be handed over to Muslims to be tried under Sharia law.

At this point it's probably as well to try and make a distinction between Islam and Islamism; between, on the one hand, a religion which is as decent and flawed and irrational as any other and, on the other, the fundamentalist lunacy that flows from that irrationality.

In Britain, which is currently sufffering from the consequnces of such lunacy, the differences have been blurred, according to Ed Husain, the author of The Islamist, a just published book about radical Islam in the UK. "We should know our Muslim from our Islamist, " he wrote recently. "Just as we don't talk to the [fascist, racist] British National Party to understand white working-class grievances, we need not engage with Islamists to comprehend Muslim suffering." In other words, don't judge the Koran by its increasingly garish cover.

It should also be said that although Muslim fundamentalism (which is another form of fascism) is one of the greatest problems facing the world today, it is matched by the Christian fundamentalism which has crept into US politics, even, indeed, into the White House.

On a visit to Egypt in late 2005, George Bush informed a group, including the then Palestinian foreign minister, Nabil Shaath, that God had told him to invade Iraq. "I am driven with a mission from God, " Bush said, according to Nabil. "God would tell me, 'George, go and fight these terrorists in Afghanistan'. And I did. And then God would tell me, 'George, go and end the tyranny in Iraq'. And I did."

Bush is no less crazy than the Muslim fundamentalists who believe that there is the one true religion and one true God, and who seek to impose a unique world view based on that contention. When fundamentalists of any hue invade countries or issue death threats against people who disagree with them, they are calling the very foundations of democracy and freedom into question.

Which is why, while religion has an important role to play for so many people, and is a support and comfort to millions, it should have no function in public life. If we must hear about people's beliefs, let it be in the music of Sinead O'Connor or in the literature of Salman Rushdie, which we can embrace or ignore as we see fit.

In the end, as Salman Rushdie once said, fundamentalism is not about religion but about power, in his case the power of some Islamists to affect lives and rights and freedom of expression through the medium of outrage.

It's time secular society fought back against fundamentalism and the fools who embrace it. Anything else is appeasement.