On the other hand, I find the following argument equally compelling
The argument you discuss an example of very weak anthropic evidence, so I don’t think it’s a good intuition pump about the validity of anthropic reasoning in general. In general anthropic evidence can be quite strong—the presumptuous philosopher thought experiment, for instance, argues for an update of a trillion to one.
However, I thought the “grabby aliens” argument was NOT based on SSA, and in fact is counter to SSA, because they’re not weighing the alien civilizations by their total populations?
I think there’s a terminological confusion here. People sometimes talk about SSA vs SIA, but in Bostrom’s terminology the two options for anthropic reasoning are SSA + SIA, or SSA + not-SIA. So in Bostrom’s terminology, every time you’re doing anthropic reasoning, you’re accepting SSA; and the main reason I linked his chapter was just to provide intuitions about why anthropic reasoning is valuable, not as an argument against SIA. (In fact, the example I quoted above has the same outcome regardless of whether you accept or reject SIA, because the population size is fixed.)
I don’t know whether Hanson is using SIA or not; the previous person who’s done similar work tried both possibilities. But either would be fine, because anthropic reasoning has basically been solved by UDT, in a way which dissolves the question of whether or not to accept SIA—as explained by Stuart Armstrong here.
The argument you discuss an example of very weak anthropic evidence, so I don’t think it’s a good intuition pump about the validity of anthropic reasoning in general. In general anthropic evidence can be quite strong—the presumptuous philosopher thought experiment, for instance, argues for an update of a trillion to one.
I think there’s a terminological confusion here. People sometimes talk about SSA vs SIA, but in Bostrom’s terminology the two options for anthropic reasoning are SSA + SIA, or SSA + not-SIA. So in Bostrom’s terminology, every time you’re doing anthropic reasoning, you’re accepting SSA; and the main reason I linked his chapter was just to provide intuitions about why anthropic reasoning is valuable, not as an argument against SIA. (In fact, the example I quoted above has the same outcome regardless of whether you accept or reject SIA, because the population size is fixed.)
I don’t know whether Hanson is using SIA or not; the previous person who’s done similar work tried both possibilities. But either would be fine, because anthropic reasoning has basically been solved by UDT, in a way which dissolves the question of whether or not to accept SIA—as explained by Stuart Armstrong here.