ALEX EVANS is a development wonk with an engaging streak of vulnerability. As an adviser on poor-world economics to Tony Blair’s government in Britain, and then a co-organiser of a UN climate-change summit, he has seen first-hand the waves of optimism and pessimism that have washed over the inner circle of politicians and bureaucrats with an interest in cooling the planet. He sensed the eager anticipation ahead of the Copenhagen summit in 2009 and the bitter disappointment at its failure. He confesses to feeling "giddy with excitement" when asked by the then UN secretary-general, Ban Ki-moon, to help prepare a global gathering on sustainability, which promised to be a phoenix rising from the ashes of Copenhagen; and recalls his dismay when a coalition including America and Brazil joined forces, as he puts it, to "block anything remotely ambitious". Compared with all that, the far more positive outcome of the Paris climate-change summit (pictured), just over a year ago, came as a blessed relief and in some ways a pleasant surprise.

Doubtless there are lots of climate-change activists who have ridden a similar roller-coaster. What makes Mr Evans a bit unusual is the diagnosis he makes of why (at least in part) Copenhagen failed and Paris succeeded. One of the problems, before the Danish disaster, was that green activists, even the most lively-minded ones, were boring people to death with pie-charts, acronyms and statistics. By the time world leaders had gathered in France, environmentalists had begun to grasp the message that they could only touch people's hearts by telling stories. In other words: by using the method of religious prophets of old, the marketing gurus of the 20th century and the science-fiction writers gazing into the future. It was a sign of the times that François Hollande, the president of France, encouraged a strong spiritual input in the summit. All these people understood that they could only grab and retain ordinary citizens' attention with good yarns: powerful, memorable, morally compelling narratives that could prompt the listener to step inside and take a stance. That is the argument Mr Evans makes in a very short, very sharp book, “The Myth Gap”.

He observes that all successful movements, including those that overturned slavery and racial discrimination, consisted of a network of small and large communities held together not by common calculations or common acceptance of certain technical facts, but by commonly-proclaimed narratives about the past and the future. In his view the political shockwaves of 2016, including Brexit and Donald Trump's victory, reflected the winning camps’ ability to tell better stories, not their superior command of facts.

The stories that particularly engage Mr Evans, as it happens, come from the religion and rituals of ancient Israel. He is interested by the ritual of atonement in the first temple of Jerusalem, and its declared purpose of healing and mending not merely anything that was amiss in human society but any damage to the web of connections linking man and the environment. As a moral tale of creation and the emergence of evil, he is less interested in the Adam-and-Eve narrative than in the story of Enoch, a figure who gets only fleeting mentions in the Hebrew scriptures but features in a mysterious sacred text that was preserved by Christians in Russia and Ethiopia. The Book of Enoch describes how bad angels corrupted human beings, tempting them to misuse knowledge and technology: a good metaphor, Mr Evans thinks, for the foolishness of modern times and the way in which whole institutions can be infected by a culture of corruption.

But to inspire people, he adds, stories cannot focus exclusively on bad guys and the terrible things they do. They must also, like the atonement ritual, hold out the dream of restoration and redemption. In climate-change terms, that could translate into a greater emphasis on success stories, including places like China's Loess Plateau, where degraded ecosystems have been repaired with spectacular results.

Mr Evans is right to stress that passionately engaged communities, including religious communities, are usually organized around stories, not around factual propositions or even common moral codes. But of course religious narratives, and the subtle differences between one version and another, can divide people as well as rally them. To this day Sunni and Shia Muslims in Iraq are inspired, at least in part, to kill one another because they have different interpretations of the battle of Karbala in the year 680. Artificially whipped-up recollections of the Battle of Kosovo in 1389 were among the factors that set Serbs and ethnic Albanians at one another's throats in the 1990s. In recent times, conflict in Northern Ireland was fueled, at least in part, by conflicting stories about the Protestant-Catholic wars of the 17th century.

Mr Evans is realistic enough to accept that for the forseeable future, there will be many passionately-told narratives in the world; he is also struck by the fact that digital animation and virtual reality make it easier than ever to invent new ones. One challenge, then, lies in fashioning stories that are good in the deepest sense, or at least in drawing good conclusions from old stories. No less important is encouraging tightly-knit communities, large and small, to listen to one another’s stories with respect and not hate.