Robert Wright in Nonzero Newsletter:
Effective altruism—EA for short—is a pretty straightforward extension of utilitarian moral philosophy and drew much of its founding inspiration from the most famous living utilitarian philosopher, Peter Singer. The basic idea is that you should maximize the amount of increased human welfare per dollar of philanthropic donation or per hour of charitable work. A classic EA expenditure is on mosquito nets: You can actually count the lives you’re theoretically saving from the ravages of malaria and compare that with the number of lives you could have saved by, say, funding a water purification project.
Longtermism, by adding all generations yet unborn to the utilitarian calculus, vastly expands the horizons of effective altruists. Instead of just scanning Earth in search of people who can be efficiently helped, they can scan eternity. That may sound like a nebulous enterprise, but it has at least one clear effect that I applaud: It can get effective altruists focused on the problem of “existential threats”—things that could conceivably wipe out the whole human species.