I agree it’s vague and controversial, but that’s OK in this case because it’s an important variable we probably use in our decisions anyway. We seek to maximize our impact, so we do some sort of search over possible plans, and a good heuristic is to contrain our search to plans that take effect before it is too late. (Of course, this gets things backwards in an important sense: Whether or not it is too late depends on whether there are any viable plans, not the other way round. But it’s still valid I think because we can learn facts about the world that make it very likely that it’s too late, saving us the effort of considering specific plans.)
I agree it’s vague and controversial, but that’s OK in this case because it’s an important variable we probably use in our decisions anyway. We seek to maximize our impact, so we do some sort of search over possible plans, and a good heuristic is to contrain our search to plans that take effect before it is too late. (Of course, this gets things backwards in an important sense: Whether or not it is too late depends on whether there are any viable plans, not the other way round. But it’s still valid I think because we can learn facts about the world that make it very likely that it’s too late, saving us the effort of considering specific plans.)