If the human race lasts as long as a typical mammalian species and our population continues at its current size, then there are 80 trillion people yet to come. Oxford philosophy professor William MacAskill says it's up to us to protect them.

In his bold new book, "What We Owe the Future," MacAskill makes a case for longtermism. He believes that how long we survive as a species may depend on the actions we take now.

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