IMAGINE a child, running barefoot through a forest, and a broken glass bottle buried just beneath the soil. What’s worse: that a present-day child steps on the shards, or that a child in 100 years from now does?
This question, posed by philosopher Derek Parfit in the 1980s, was intended to clarify our moral obligations towards unborn generations. Knowingly risking harm to a future person, he argued, is just as bad whether it is today or in a century.
Parfit’s ideas inspired a branch of moral philosophy called longtermism. It rests on three premises: future people matter, there could be a lot of them and we have the power to make their lives better or worse. Ensuring the future goes well should therefore be a key moral priority of our time.
All of which seems reasonable, at first glance: it apparently promotes the universal values of stewardship, the duty to posterity and being a “good ancestor”. But longtermism has proven controversial, with some critics arguing that it is a “dangerous ideology” that permits or even encourages the suffering of people alive today.
Is that fair? To make up your own mind, the first thing you need to know is that longtermism comes in different flavours. Many of the most strident criticisms focus on the implications of “strong longtermism”, a variant introduced in a 2021 paper by the University of Oxford’s Hilary Greaves and William MacAskill, which says that it should be the top moral priority of our time.
This would have striking consequences for how money is spent in the real world. Indeed, it is already having an influence. …