I agree that there are challenges for each of them in the case of an infinite number of people. My impression is that total utilitarianism can handle infinite cases pretty respectably, by supplementing the standard maxim of maximizing utility with a dominance principle to the effect of 'do what's best for the finite subset of everyone that you're capable of affecting', though it also isn't something I've thought about too much either. I initially was thinking that average utilitarians can't make a similar move without undermining it's spirit, but maybe they can. However, if they can, I suspect they can make the same move in the finite case ('just focus on the average among the population you can affect') and that will throw off your calculations. Maybe in that case, if you can only affect a small number of individuals, the threat from solipsism can't even get going.
In any case, I would hope that SIA is at least able to accommodate an infinite number of possible people, or the possibility of an infinite number of people, without becoming useless. I take it that there are an infinite number of epistemically possible people, and so this isn't just an exercise.
Interesting application of SIA, but I wonder if it shows too much to help average utilitarianism.
SIA seems to support metaphysical pictures in which more people actually exist. This is how you discount the probability of solipsism. But do you think you can simultaneously avoid the conclusion that there are an infinite number of people?
This would be problematic: if you're sure that there are an infinite number of people, average utilitarianism won't offer much guidance because you almost certainly won't have any ability to influence the average utility.
Nice summary of the issues.A couple of related thoughts:There are some reasons to think that insects would not be especially harmed by factory farming, in the way that vertebrates are. It is plausible that the largest source of suffering in factory farms come from the stress produced by lack of enrichment and unnatural and overcrowded conditions. Even if crickets are phenomenally conscious AND can suffer, they might not be capable of stress or capable of stress in the same sort of dull over-crowded conditions as vertebrates. Given their ancient divergence in brain structures, their very different life styles, and their comparatively minuscule brains, it is reasonable to be skeptical that they feel environment induced stress. Death is conceivably such a short portion of their life that even a relatively painful death won't tip the balance.If crickets are not harmed by the conditions of factory farms, they might instead benefit from factory farming. It seems possible that the average factory farmed cricket might have a net positive balance of good experiences vs bad experiences. In that case, it might be better to raise crickets in factory farm conditions than to produce equivalent amounts of non-sentient meat alternatives. The risks are not entirely on the farming side.