Before August 2022, I had to explain who Will MacAskill was when mentioning him to friends and family. After August 2022, that’s unnecessary. The month saw MacAskill, a professor of philosophy at Oxford and a grantmaker for billionaire Sam Bankman-Fried’s foundation, become a New York Times bestselling author after the release of his book What We Owe the Future as well as the subject of profiles in the New Yorker and Time.

The book pushed effective altruism, a term and idea that MacAskill helped originate over a decade ago, into the American mainstream. In doing so, it earned a new audience for concepts MacAskill had worked on for years — and brought novel dangers.

MacAskill’s book is a passionate argument for longtermism, the view that the trillions of humans and animals who may live in the future have moral weight and that people alive right now should try to help those future beings to live good lives. It’s a powerful but inevitably controversial idea, as Sigal Samuel has explained in a piece for Vox, one that forces us to ask hard questions about what kind of world we want, the nature of morality, and whether improving the far future is even possible.

The publication of What We Owe the Future is just the beginning of the debate over longtermism, but the most promising aspect of the book’s launch wasn’t the spread of its main idea. It was MacAskill’s ability to force the question of “how to do the most good” onto the public agenda in an unprecedented way. He was able to pause a relentless news cycle for a brief moment and ask a global audience to think seriously about their moral purpose and whether they could live a more ethical life.

In some ways, this kind of grassroots moral renewal was the original purpose of effective altruism as a movement, which began with the spread of a pledge committing to donate at least 10 percent of one’s income to effective charities. MacAskill (and other leaders like Toby Ord and Julia Wise) deserve credit for that movement’s spread and success to date, with the book launch only the latest and greatest marketing success.

Going forward, though, the actual substance of longtermism will be increasingly put to the test. Can MacAskill and other longtermists identify promising methods to affect the longterm future? Can the worldview highlight new causes or just reiterate old ones like preventing nuclear war and pandemics? Will funders like MacAskill himself face hard trade-offs between helping people alive now versus building a brighter future? These are tough questions, and MacAskill will be a key figure answering them.