So, “maximize expected value”, say, is a quantity we could define. It just doesn’t help us very much, because whenever you try to do something specific you’re still virtually as far away as you had been. On the other hand, if you set some more concrete objective, like maximize the number of people in this room, or something like that, we can now easily tell like how many people there are, and we have ideas about how we could maximize it. So any particular action we think of we might easily see how it fares on this objective of maximizing the people in this room. However, we might feel it’s very difficult to get strong reasons for knowing whether more people in this room is better, or whether there is some inverse relationship. A good signpost would strike a reasonable compromise between being visible from afar and also being such that we can have strong reason to be sure of its sign.

Nick Bostrom, Crucial Considerations and Wise Philanthropy, Good Done Right conference, 2014

Added to diary 12 December 2018