If a catastrophe should really dominate our thinking, it will not be because of the people it kills. There will be other harms, of course. But the effect that seems the most potentially harmful is the huge number of people whose existence might be prevented by a catastrophe. If we become extinct within the next few thousand years, that will prevent the existence of tens of trillions of people, as a very conservative estimate. If those nonexistences are bad, then this is a consideration that might dominate our calculations of expected utility.

John Broome, ‘A Small Chance of Disaster’, European Review, vol. 21, no. S1 (July, 2013), p. 830