Can doing good be a matter of evidence and arithmetic?

Effective altruists say yes, as far as possible, and their critics ask what the arithmetic leaves out. Effective altruism is a 21st-century movement that advocates impartially calculating benefits and prioritizing causes to do the greatest good, "using evidence and reason to figure out how to benefit others as much as possible". The name was coined in 2011, and the philosophers most associated with it are Peter Singer, Toby Ord and William MacAskill.

Impartiality is the defining feature: it considers everyone's interests equally, wherever they live. Popular priorities include global health and development, animal welfare, and risks to humanity's long-term future. In practice, that means evidence. The charity evaluator GiveWell was founded in 2007, and randomized trials in Kenya by Michael Kremer and Rachel Glennerster found that textbooks, flip charts and smaller classes did not raise school attendance, but treating intestinal worms did. Members of Giving What We Can pledge at least 10% of their future income to what they judge the most effective causes.

The long view is more contested. Longtermism argues that "distance in time is like distance in space", so future people's welfare matters as much as ours. That makes tiny reductions in existential risk look enormous, though, as Gideon Lewis-Kraus reported, nobody in the EA community openly endorses the most extreme conclusion.

Critics push on three fronts. Some argue that impartial, detached giving is weaker than benevolence built on reciprocity and face-to-face ties. Others say that when everything is measured, justice, fairness and equality get left in the sidelines, or that EA favours incremental over systemic change. And after the 2022 collapse of Sam Bankman-Fried's exchange FTX, the philosopher Leif Wenar argued that the case typified a movement focused on expected value without adequately weighing risk and harm.