Francois Hollande honours Amartya Sen with the Legion d’Honneur in New Delhi in 2013 ©Swarup/Rex/Shutterstock

Amartya Sen is an eminently reasonable man. Over six decades as an economist and political theorist—he won the Nobel Prize in 1998—the 83-year-old has kept faith with rational thinking. This is as much to do with personal experience as intellectual preference. As a boy growing up in Bengal, Sen saw a bleeding labourer stumble into his garden. He was a Muslim who had been stabbed by Hindus. “Aside from being a veritable nightmare, the event was profoundly perplexing,” Sen wrote in his Identity and Violence (2006). It provoked revulsion, but also consideration. Through his career, even while working on emotive subjects like famine, poverty, justice and inequality, he has maintained a calm equilibrium.

When I spoke to him in London about the emotions unleashed by Donald Trump, Sen put things in perspective. “There is nothing new or extraordinary in his rejection of  reason,” he said, in the Bengali accent that western universities have never drummed out of him. “Even the French Revolution, which was so enormously well-backed by reason, led to a reign of terror.” One victim was the philosopher the Marquis de Condorcet, whose theories influenced Sen’s work on social choice. Under threat from the Revolutionary regime, Condorcet committed suicide in 1794.

The US president keenly targets his enemies—if only via Twitter. “He has managed to unleash a kind of thinking which drew more on prejudice than on cool reasoning,” said Sen, with magnificent understatement. “And I would apply this to Brexit,” he continued, “where some of the sentiments of hatred of foreigners came into the story in a big way.” He quotes Thomas Jefferson: “Eternal vigilance is the price of liberty.” Without  it, democracy can be “taken over by forces that play up other things, especially hatred of particular communities.”

His home nation India has recently taken a nasty turn in that direction. When the Prime Minister Narendra Modi was governor of Gujarat in 2002, he was accused of stoking anti-Muslim riots that led to 2,000 deaths. Sen took a stand against Modi in 2014, telling me with relish how he “flew from Boston to New York, New York to New Delhi, New Delhi to Calcutta, and took a car to my village to vote against Mr Modi’s BJP candidates.” His criticism…

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