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For example, to the extent "the world" means its human population, Noora Health (http://noorahealth.org ) literally saves the world. Surely it's good that optimistic people want to work for them rather than just giving up on the idea of a job making the world better.
Or maybe it would be better to save the world in a physical sense (from global warming) by working on new energy sources, e.g. at Helion (http://www.helionenergy.com ). There is no one best answer for everyone, but surely some answers are better than others.
I've been bothered of late how much of public debate/conversation is only about what changes in public policy would improve the world. So little time is spent discussing how the world could be better if some non-existent tech or private organization suddenly existed
Or as you point out, how some private organizations are already improving the world and where the marginal benefit of doing more is still massive
Education is another fast growing, make-the-world-better space with almost infinite need, purpose, and meaning
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