Against Empathy: The Case for Rational Compassion. By Paul Bloom. Ecco; 304 pages; $26.99. Bodley Head; 290 pages; £18.99.

IN an age of partisan divides it has become popular to assert that the wounds of the world would heal if only people made the effort to empathise more with each other. If only white police officers imagined how it feels to be a black man in America; if only black Americans understood the fears of the man in uniform; if only Europeans opposed to immigration walked a mile in the shoes of a Syrian refugee; if only tree-hugging liberals knew the suffering of the working class.

Barack Obama warned of an empathy “deficit” in 2006, and did so again in his valedictory speech in January: “If our democracy is to work in this increasingly diverse nation,” he said, “each one of us must try to heed the advice of one of the great characters in American fiction, Atticus Finch, who said, ‘You never really understand a person until you consider things from his point of view...until you climb into his skin and walk around in it.’”

It is a piece of generous, high-minded wisdom with which few would dare to disagree. But Paul Bloom, a psychologist at Yale University, does disagree. His new book, “Against Empathy”, makes the provocative argument that the world does not need more empathy; it needs less of it. People are bingeing on a sentiment that does not, on balance, make the world a better place. Empathy is “sugary soda, tempting and delicious and bad for us”. In its stead, Mr Bloom prescribes a nutritious diet of reason, compassion and self-control.

To be clear, Mr Bloom is not against kindness, love or general good will toward others. Nor does he have a problem with compassion, or with “cognitive” empathy—the ability to understand what someone else is feeling. His complaint is with empathy defined as feeling what someone else feels. Though philosophers at least as far back as Adam Smith have held it up as a virtue, Mr Bloom says it is a dubious moral guide. Empathy is biased: people tend to feel for those who look like themselves. It is limited in scope, often focusing attention on the one at the expense of the many, or on short-term rather than long-term consequences. It can incite hatred and violence—as when Donald Trump used the example of Kate Steinle, a woman murdered by an undocumented immigrant, to drum up anti-immigrant sentiment, or whenIslamic State fighters point to instances of Islamophobia to encourage terrorist attacks. It is innumerate, blind to statistics and to the costs of saccharine indulgence.

Empathy can be strategically useful to get people to do the right thing, Mr Bloom acknowledges, and it is central to relationships (though even here it must sometimes be overridden, as any parent who takes a toddler for vaccinations knows). But when it comes to policy, empathy is too slippery a tool. “It is because of empathy that citizens of a country can be transfixed by a girl stuck in a well and largely indifferent to climate change,” he writes. Better to rely on reason and cost-benefit analysis. As rational arguments for environmental protection or civil rights show, morality is possible without sentimental appeals to individual suffering. “We should aspire to a world in which a politician appealing to someone’s empathy would be seen in the same way as one appealing to people’s racist bias,” Mr Bloom writes. Racism, like anger or empathy, is a gut feeling; it might be motivating, but that kind of thinking ultimately does more harm than good.

That is a radical vision—and like many Utopias, one with potentially dystopian consequences. Unless humans evolve into something like the Vulcans from “Star Trek”, guided purely by logic, it is also unimaginable. Reason should inform governance, but people tend to be converted to a cause—gay marriage, for instance—by emotion. Yet Mr Bloom’s point is a good one: empathy is easily exploited, marshalled on either side of the aisle to create not a bridge but an impasse of feelings. In a time of post-truth politics, his book offers a much-needed call for facts.