As a child, my wife hated her school and wished she could leave. Years later, when she was in her twenties, she disclosed this unhappy fact to her parents, and her mother was aghast: 'But darling, why didn't you come to us and tell us?' Lalla's reply is my text for today: 'But I didn't know I could.'

I didn't know I could.

I suspect — well, I am sure — that there are lots of people out there who have been brought up in some religion or other, are unhappy in it, don't believe it, or are worried about the evils that are done in its name; people who feel vague yearnings to leave their parents' religion and wish they could, but just don't realize that leaving is an option. If you are one of them, this book is for you. It is intended to raise consciousness — raise consciousness to the fact that to be an atheist is a realistic aspiration, and a brave and splendid one. You can be an atheist who is happy, balanced, moral, and intellectually fulfilled. That is the first of my consciousness-raising messages. I also want to raise consciousness in three other ways, which I'll come on to.

In January 2006 I presented a two-part television documentary on British television (Channel Four) called Root of All Evil? From the start, I didn't like the title. Religion is not the root of all evil, for no one thing is the root of all anything. But I was delighted with the advertisement that Channel Four put in the national newspapers. It was a picture of the Manhattan skyline with the caption 'Imagine a world without religion.' What was the connection? The twin towers of the World Trade Center were conspicuously present.

Imagine, with John Lennon, a world with no religion. Imagine no suicide bombers, no 9/11, no 7/7, no Crusades, no witch-hunts, no Gunpowder Plot, no Indian partition, no Israeli/Palestinian wars, no Serb/Croat/Muslim massacres, no persecution of Jews as 'Christ-killers', no Northern Ireland 'troubles', no 'honour killings', no shiny-suited bouffant-haired televangelists fleecing gullible people of their money ('God wants you to give till it hurts'). Imagine no Taliban to blow up ancient statues, no public beheadings of blasphemers, no flogging of female skin for the crime of showing an inch of it. Incidentally, my colleague Desmond Morris informs me that John Lennon's magnificent song is sometimes performed in America with the phrase 'and no religion too' expurgated. One version even has the effrontery to change it to 'and one religion too'.

Perhaps you feel that agnosticism is a reasonable position, but that atheism is just as dogmatic as religious belief? If so, I hope Chapter 2 will change your mind, by persuading you that 'the God Hypothesis' is a scientific hypothesis about the universe, which should be analysed as sceptically as any other. Perhaps you have been taught that philosophers and theologians have put forward good reasons to believe in God. If you think that, you might enjoy Chapter 3 on 'Arguments for God's existence' — the arguments turn out to be spectacularly weak. Maybe you think it is obvious that God must exist, for how else could the world have come into being? How else could there be life, in all its rich diversity, with every species looking uncannily as though it had been 'designed'? If your thoughts run along those lines, I hope you will gain enlightenment from Chapter 4 on 'Why there almost certainly is no God'. Far from pointing to a designer, the illusion of design in the living world is explained with far greater economy and with devastating elegance by Darwinian natural selection. And, while natural selection itself is limited to explaining the living world, it raises our consciousness to the likelihood of comparable explanatory 'cranes' that may aid our understanding of the cosmos itself. The power of cranes such as natural selection is the second of my four consciousness-raisers.

Perhaps you think there must be a god or gods because anthropologists and historians report that believers dominate every human culture. If you find that convincing, please refer to Chapter 5, on 'The roots of religion', which explains why belief is so ubiquitous. Or do you think that religious belief is necessary in order for us to have justifiable morals? Don't we need God, in order to be good? Please read Chapters 6 and 7 to see why this is not so. Do you still have a soft spot for religion as a good thing for the world, even if you yourself have lost your faith? Chapter 8 will invite you to think about ways in which religion is not such a good thing for the world.

If you feel trapped in the religion of your upbringing, it would be worth asking yourself how this came about. The answer is usually some form of childhood indoctrination. If you are religious at all it is overwhelmingly probable that your religion is that of your parents. If you were born in Arkansas and you think Christianity is true and Islam false, knowing full well that you would think the opposite if you had been born in Afghanistan, you are the victim of childhood indoctrination. Mutatis mutandis if you were born in Afghanistan.

The whole matter of religion and childhood is the subject of Chapter 9, which also includes my third consciousness-raiser. Just as feminists wince when they hear 'he' rather than 'he or she', or 'man' rather than 'human', I want everybody to flinch whenever we hear a phrase such as 'Catholic child' or 'Muslim child'. Speak of a 'child of Catholic parents' if you like; but if you hear anybody speak of a 'Catholic child', stop them and politely point out that children are too young to know where they stand on such issues, just as they are too young to know where they stand on economics or politics. Precisely because my purpose is consciousness-raising, I shall not apologize for mentioning it here in the Preface as well as in Chapter 9. You can't say it too often. I'll say it again. That is not a Muslim child, but a child of Muslim parents. That child is too young to know whether it is a Muslim or not. There is no such thing as a Muslim child. There is no such thing as a Christian child.

Chapters 1 and 10 top and tail the book by explaining, in their different ways, how a proper understanding of the magnificence of the real world, while never becoming a religion, can fill the inspirational role that religion has historically — and inadequately — usurped.

My fourth consciousness-raiser is atheist pride. Being an atheist is nothing to be apologetic about. On the contrary, it is something to be proud of, standing tall to face the far horizon, for atheism nearly always indicates a healthy independence of mind and, indeed, a healthy mind. There are many people who know, in their heart of hearts, that they are atheists, but dare not admit it to their families or even, in some cases, to themselves. Partly, this is because the very word 'atheist' has been assiduously built up as a terrible and frightening label. Chapter 9 quotes the comedian Julia Sweeney's tragi-comic story of her parents' discovery, through reading a newspaper, that she had become an atheist. Not believing in God they could just about take, but an atheist! An ATHEIST? (The mother's voice rose to a scream.)

I need to say something to American readers in particular at this point, for the religiosity of today's America is something truly remarkable. The lawyer Wendy Kaminer was exaggerating only slightly when she remarked that making fun of religion is as risky as burning a flag in an American Legion Hall.¹ The status of atheists in America today is on a par with that of homosexuals fifty years ago. Now, after the Gay Pride movement, it is possible, though still not very easy, for a homosexual to be elected to public office. A Gallup poll taken in 1999 asked Americans whether they would vote for an otherwise well-qualified person who was a woman (95 per cent would), Roman Catholic (94 per cent would), Jew (92 per cent), black (92 per cent), Mormon (79 per cent), homosexual (79 per cent) or atheist (49 per cent). Clearly we have a long way to go. But atheists are a lot more numerous, especially among the educated elite, than many realize. This was so even in the nineteenth century, when John Stuart Mill was already able to say: 'The world would be astonished if it knew how great a proportion of its brightest ornaments, of those most distinguished even in popular estimation for wisdom and virtue, are complete sceptics in religion.'