Having children or raising them involves enormous sacrifice of time, money, effort and energy. Religious people understand the concept of sacrifice. We live by it. It’s part of our lives. But people in a secular, consumerist, individualist culture find it much harder to live by sacrifice. Nothing in the culture says sacrifice, and throughout history that is the reason why when a culture begins to lose its faith, its birth rate starts to decline. This is not just happening now. It has happened throughout history. It happened in Ancient Greece in the second century BCE. It happened in Ancient Rome. It happened in Renaissance Italy. The people who’ve done the research say there is no case on record in which a secular society has been able to maintain its birth rates. Within a century, every society, when it becomes secularised, starts to decline demographically. So the 21st century is going to be more religious than the 20th century even if not one person changes his or her mind from being non-religious to religious. It will happen for a simple reason: throughout the world today the more religious you are, the more children you have.

This is a global demographic fact. This, incidentally, explains why levels of immigration to Europe, which has been the big storm hitting Europe for the last decade, are so high, higher than they’ve ever been before in history. Europe hasn’t admitted immigrants because it’s more generous than any time in the past, but because it has lower birth rates than in the past. Immigration is the only way Europe can counter its declining and ageing populations. Europe will die because it wasn’t mindful. It misread Charles Darwin, took him as the patron saint of atheists and failed to realise that actually he was the prophet of reproductive success, of having enough faith to bring a child into the world. That is how religion, or rather the loss of religion, is causing the contraction of the family.

Now society. I want to stay with Darwin for a moment. There’s a famous problem that Darwin realised with his own theory. He was very honest and admitted this was a problem for his theory. It threatened to undermine the whole principle of natural selection.

I can at best explain Darwin’s doubt in terms of The Imitation Game, the film about Alan Turing and how they broke the German codes in the war. Benedict Cumberbatch plays Turing, alongside Keira Knightley. At one point in the film, she encourages Turing to tell a joke, which he does as badly as I do. The joke he tells is about two explorers in the jungle. Suddenly, they hear the sound of a lion. The first one runs off to find a place where both of them can hide. The second one starts putting on his running shoes. The first one says to the second one, “You’re crazy. You can’t run faster than the lion.” The second one says, “I don’t need to run faster than the lion. I just need to run faster than you.” Here is the classic tension between the altruist, who wants to save both of them, and the survivalist, who just wants to escape himself. Now, which of the two gets eaten by the lion? The altruist.