Today’s show is built around three simple sentences: “Future people count. There could be a lot of them. And we can make their lives better.” Those sentences form the foundation of an ethical framework known as “longtermism.” They might sound obvious, but to take them seriously is a truly radical endeavor — one with the power to change the world and even your life.

That second sentence is where things start to get wild. It’s possible that there could be tens of trillions of future people, that future people could outnumber current people by a ratio of something like a million to one. And if that’s the case, then suddenly most of the things we spend most of our time arguing about shrink in importance compared with the things that will affect humanity’s long-term future.

William MacAskill is a professor of philosophy at Oxford University, the director of the Forethought Foundation for Global Priorities Research and the author of the forthcoming book, “What We Owe the Future,” which is the best distillation of the longtermist worldview I’ve read. So this is a conversation about what it means to take the moral weight of the future seriously and the way that everything — from our political priorities to career choices to definitions of heroism — changes when you do.

We also cover the host of questions that longtermism raises: How should we weigh the concerns of future generations against those of living people? What are we doing today that future generations will view in the same way we look back on moral atrocities like slavery? Who are the “moral weirdos” of our time we should be paying more attention to? What are the areas we should focus on, the policies we should push, the careers we should choose if we want to guarantee a better future for our posterity?

And much more.

Mentioned:

"Is A.I. the Problem? Or Are We?" by The Ezra Klein Show

"How to Do The Most Good" by The Ezra Klein Show

"This Conversation With Richard Powers Is a Gift" by The Ezra Klein Show

Book Recommendations:

“Moral Capital” by Christopher Leslie Brown

“The Precipice” by Toby Ord

“The Scout Mindset” by Julia Galef

Thoughts? Guest suggestions? Email us at ezrakleinshow@nytimes.com.

You can find transcripts (posted midday) and more episodes of “The Ezra Klein Show” at nytimes.com/ezra-klein-podcast, and you can find Ezra on Twitter @ezraklein. Book recommendations from all our guests are listed at https://www.nytimes.com/article/ezra-klein-show-book-recs.

“The Ezra Klein Show” is produced by Annie Galvin and Rogé Karma; fact-checking by Michelle Harris, Mary Marge Locker and Kate Sinclair; original music by Isaac Jones; mixing by Sonia Herrero and Isaac Jones; audience strategy by Shannon Busta. Special thanks to Kristin Lin and Kristina Samulewski.

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What do we owe future humans?