A – Definition: The greatest good for the greatest number of people; sacrifices are OK
B – Justifications:
Life is a pre-requisite to ethics Bostrom1
Continuity is as important to our commitment to the project of the future of humanity as it is to our commitment to the projects of our own personal futures. Just as the shape of my whole life, and its connection with my present and past, have an interest that goes beyond that of any isolated experience, so too the shape of human history over an extended period of the future, and its connection with the human present and past, have an interest that goes beyond that of the (total or average) quality of life of a population- at-a-time, considered in isolation from how it got that way. We owe, I think, some loyalty to this project of the human future. We also owe it a respect that we would owe it even if we were not of the human race ourselves, but beings from another planet who had some understanding of it. (28: 472-473)
Utilitarianism is most consistent with human psychology Nagel2
When the objective self contemplates pain, it has to do so through the perspective of the sufferer, and the sufferer’s reaction is very clear. Of course he wants to be rid of this pain unreflectively—not because he thinks it would be good to reduce the amount of pain in the world. But at the same time his awareness of how bad it is doesn’t essentially involve the thought of it as his. The desire to be rid of pain has only the pain as its object. This is shown by the fact that it doesn’t even require the idea of oneself in order to make sense: if I lacked or lost the conception of myself as distinct from other possible or actual persons, I could still apprehend the badness of pain, immediately. So when I consider it from an objective standpoint, the ego doesn’t get between the pain and the objective self. My objective attitude toward pain is rightly taken over from the immediate