The humorist Alan Coren was told by his publisher that if he wanted to write a bestseller it should be about sport or pets. So he wrote a book called Golfing for Cats. Today I suspect his publisher would tell him to attack religion. Atheism sells.

First The End of Faith by Sam Harris was a success in the US. Then came Daniel Dennett’s Breaking the Spell, Richard Dawkins’s The God Delusion and A. C. Grayling’s Against all Gods. And now Christopher Hitchens’s God is not Great is high in the charts both sides of the Atlantic.

There have been, of course, various ecclesiastical ripostes, usually that atheism is itself a faith and you can have secular fundamentalists as well as religious ones. This is fine if we enjoy knockabout polemics, but if we are honest, it’s not good enough.

There is a story told about the 1st-century Jewish teacher Yochanan ben Zakkai. A Roman challenged him about a Jewish ritual. Pure superstition, he said. Not so, said the rabbi, and gave him an answer that made sense in terms of his questioner’s beliefs. The Roman went away satisfied. But the rabbi’s disciples said: “You answered him. What will you answer us?”

That is the real question. Atheism does not come from nowhere. Agnosticism and indifference do; people drift, religion ceases to inspire, there are other things to do. Atheism is different. It is a form of protest. Something goes badly wrong in religious life, and people feel moved to write books saying, essentially, “Not in my name”. When that happens, mere apologetics is not enough. When the debate is over, something inside the believer’s soul refuses to stay silent. “You answered him. What will you answer us?”

Secularisation, the great movement of the European mind that began in the 17th century, did not begin because people stopped believing in God. The movement’s intellectual heroes, Newton and Descartes, believed in God very much indeed.

What they lost faith in was the ability of religious people to live peaceably together. Catholics and Protestants had been fighting one another across Europe in what Hobbes called “the war of every man against every man”. There had to be another way. So, first science, then philosophy, politics and culture were rebuilt on foundations that did not depend on doctrine or dogma but instead on experiment and observation, reason and inference.

As then, so now. Sunni and Shia fight in the Middle East, as do Muslims and Hindus in Kashmir, Buddhists and Hindus in Sri Lanka, and Muslims and Jews in Israel. Two things have happened in our postmodern, postCold War constellation. Religion, often as the outer clothing of ethnicity, has returned to the political arena. And religions still do not know how to live together in peace.

In one sense, then, we have been here before. But in another, we haven’t. That’s not just because our powers of destruction have grown, but because global communications technology means that conflict anywhere can be broadcast everywhere. Battles being fought thousands of miles away are transmitted throughout the world, creating tensions in university campuses, charities and churches, polarising opinion, wrecking friendships and dividing societies.

That’s when people start writing books about atheism and they become bestsellers. For the great strength of religion is that it creates communities, and its great weakness is that it divides communities. The two go hand in hand. For every “us” there is a “them”, and the stronger the togetherness within, the deeper the estrangement without. What binds also separates. It always did.

The real battle, and it applies to secular and religious alike, is: can we love, not hate, the people not like us? We are tribal animals. We are hardwired for conflict. Sociobiologists call this genetic coding, Christians, original sin, Jews, the evil inclination. The belief that unites us is that instinct is not the final word. Selfish genes can produce selfless people. Is that miracle or mere chance? Loving creator or blind watchmaker? That is an important question. But the urgent one is: can we, believer and nonbeliever, join hands to become agents for peace against those who seek to globalise war?

Rabbi Sir Jonathan Sacks is the Chief Rabbi of the United Hebrew Congregations of the Commonwealth