When I was a student I sold Christmas cards to raise money for UNICEF. To potential donors sipping ale in English pubs, I’d stress that for less than the price of a pint they could pay for a vaccine shot that might save the life of a child in Africa. Many reached for their wallets, but I remember one who said, in a rather peeved voice: “Why don’t you raise money for British children?”

It is a fair question. I was taking a hyper-rational approach to charity: the same donation can relieve far more suffering in a poor country than in a rich one. But many people feel more empathy for those closer by. In “Bleak House” Charles Dickens mocked a character called Mrs Jellyby, who was obsessed with helping the inhabitants of Borrioboola-Gha, a fictional sub-Saharan locale, while neglecting her own home and children.

I wonder what Dickens—let alone the man in that pub—would have made of the “effective altruists” (EAs) who now dominate Silicon Valley. As we report this week, their philosophy is the biggest idea of this century so far. And it takes the Mrs Jellyby principle to extremes. Not only do far-away people have the same claim on our goodwill as those standing next to us. Many EAs think we should care—a lot—about the billions or trillions of people who may be born in the distant future. Some also think that, because animals can suffer, we should worry as much about prawns as we do about people.

Our cover package explores these ideas. Only a few people are EAs, but they are hugely influential, since they staff the most advanced artificial-intelligence companies. Some of their insights are sound. It really is better if charity is cost-effective, and we really should take seriously the possibility that AI could go rogue and do immense harm. But sometimes their logic leads them to odd places. If your moral calculations depend on predicting what the world will be like in the year 2300, there is a good chance they will be hooey. And if you are both powerful and utterly convinced you know what’s best for humanity—well, that combination didn’t work out so well during some of the high-minded revolutions of the past, from France’s in 1789 to Russia’s in 1917.

On The Insider this week, my colleagues are talking about tax. A fiscal hurricane is approaching. Rich countries are dangerously indebted, and AI may be about to wallop their main source of revenue: human workers. Our editor-in-chief, Zanny Minton Beddoes, dials in from America to discuss what governments can do to prepare. You can tune in now.