“In ecological terms, it is not a human that is remarkable, but humanity,” Ord writes, in his book. And yet it’s easy for humanity’s aims to be undermined by the short-term political calculations and selfish desires of individuals. We are a blip, Ord argues, in a chain of human life that stretches back two hundred thousand years, and that could in theory extend for hundreds of thousands, if not millions, more. One would have to be ruinously shortsighted or grotesquely narcissistic to risk obliterating all of that. And yet that is how we often seem to be.