William MacAskill, a professor of philosophy at Oxford University, is the author of What We Owe the Future." You can get a pretty good idea of his argument by reading MacAskill's guest essay in the August 5, 2022, edition of The New York Times. The Times has headlined MacAskill's essay, "The Case for Longtermism." If you'd like to learn more about MacAskill, you might also want to click the following link. That link will take you to a New Yorker profile of MacAskill, "The Reluctant Prophet of Effective Altruism."
Morality, at its core, is about putting ourselves in others’ shoes and treating their interests as we do our own. When we do this at the full scale of human history, the future — where almost everyone lives and where almost all potential for joy and misery lies — comes to the fore.
If you knew you were going to live all these future lives, what would you hope we do in the present? How much carbon dioxide would you want us to emit into the atmosphere? How careful would you want us to be with new technologies that could destroy, or permanently derail, your future? How much attention would you want us to give to the impact of today’s actions on the long term?
These are some of the questions that motivate longtermism: the idea that positively influencing the long-term future is a key moral priority of our time.