Sure. I’ll use traditional total act-utilitarianism defined as follows as the example here so that it’s clear what we are talking about:
Traditional total act-utilitarianism: An act is right if and only if it results in a sum of well-being (positive well-being minus negative well-being) that is at least as great as that resulting from any other available act.
I gather the metaethical position you describe is something like one of the following three:
(1) When I say ‘I think utilitarianism is right’ I mean ‘I think that after I reach reflective equilibrium I will think that any act I perform is right if and only if it results in a sum of well-being (positive well-being minus negative well-being) that is at least as great as that resulting from any other available act.’
This (1) was about which of your actions will be right. Alternatively, the metaethical position could be as follows:
(2) When I say ‘I think utilitarianism is right’ I mean ‘I think that after I reach reflective equilibrium I will think that any act anyone performs is right if and only if it results in a sum of well-being (positive well-being minus negative well-being) that is at least as great as that resulting from any other available act.’
Or perhaps formulating it in terms of want or preference instead of rightness, like the following, better describes your metaethical position (using utilitarianism as just an example):
(3) When I say ‘I think utilitarianism is right’ I mean ‘I think that after I reach reflective equilibrium I will want or have a preference for that everyone act in a way that results in a sum of well-being (positive well-being minus negative well-being) that is at least as great as that resulting from any other available act.’
My impression is that in the academic literature, metaethical theories/positions are usually, always or almost always formulated as general claims about what, for example, statements such as ‘one ought to be honest’ means; the metaethical theories/position do not have the form ‘when I say “one ought to be honest” I mean …’ But, sure, talking, as you do, about what you mean when you say ‘I think utilitarianism is right’ sounds fine.
The new version of your thought experiment sounds fine, which I gather would go something like the following:
Suppose almost all humans adopt utilitarianism as their moral philosophy and fully colonize the universe, and then someone invents the technology to kill humans and replace humans with beings of greater well-being. (Assume it would be optimal, all things considered, to kill and replace humans.) Utilitarianism seems to imply that at least humans who are utilitarians should commit mass suicide (or accept being killed) in order to bring the new beings into existence, because that’s what utilitarianism implies is the optimal and hence morally right action in that situation.
A few updates: I have e-mailed the Open Philanthropy Project to ask about their activities. In particular about anyone at the Open Philanthropy Project trying to influence which ideas about, for example, moral philosophy, value theory or the value of the future, that a grant recipient or potential grant recipient talks or writes about in public. I have also asked whether I can share their replies in public, so hopefully there will be more public information about this. They have not replied yet but I have elaborated on this issue in the following section: https://www.simonknutsson.com/problems-in-effective-altruism-and-existential-risk-and-what-to-do-about-them/#Troublesome_work_behind_the_scenes_including_censoring_research_and_suppressing_ideas_and_debates
I have e-mailed with Bostrom about his claim that his “Undergraduate performance set national record in Sweden” and I have talked to the university he studied at. Again, this is a less important issue but it looks strange to me, it looks like a part of a broader pattern, and it feels valuable to check it. My latest published info on the issue can be found at https://www.simonknutsson.com/problems-in-effective-altruism-and-existential-risk-and-what-to-do-about-them/#Potentially_dishonest_self-promotion. A part of the info is the following: On Oct. 23, 2019, Bostrom replied and gave me permission to share his reply in public, the relevant part of which reads as follows:
A part of my e-mail reply to Bostrom on Oct. 24, 2019:
Information about university studies seems publicly available in Sweden. When I called the University of Gothenburg on Oct. 21, 2019, the person there was not aware of any such national records and said they have the following information for Niklas Boström, born 10 March 1973: One bachelor’s degree (Swedish: fil. kand.) from University of Gothenburg awarded in January 1995. Coursework included theoretical philosophy. One master’s degree (Swedish: magister or fil. mag.) from Stockholm University. He also did some additional coursework. He started to study at university in Lund in fall 1992. I asked Bostrom whether this is him but he did not reply. More information that I noted from my call with the university include that the person could see information from different universities in Sweden, and there are in total 367.5 higher education credits in the system (from different Swedish universities) for Boström, according to the current method for counting credits. 60 credits is a normal academic year (assuming one does not, e.g., take summer courses). Boström bachelor’s degree corresponds to 180 credits, which is the exact requirement for a bachelor’s degree. The total number of credits (367.5) corresponds to 6.125 years of full-time study (again, assuming, e.g., no summer courses or extra evening courses). According to the university, he started studying in 1992 and, according to Bostrom’s CV, he studied at Stockholm University until 1996. I asked Bostrom and I gather he confirmed that he only has one bachelor’s degree. Overall, I doubt he set such a record (I think no one knows, including Bostrom himself), and I think he presents the situation in a misleading way.