Ah, I see what you're getting at. But it is not that I was trying to emphasize the possibility that there cannot be non-human minds in order to argue in favor of that hypothesis. Rather, I was pointing out that whether CEV is 'relative' or not (for purposes of this discussion) is an empirical question. For reference, I would not guess that non-human minds are physically impossible (I'd assign significantly less than 10% probability to that hypothesis).