You want them to have proven it? How would they go about testing their null hypotheses? Can they really have searched everywhere in the universe, including preposterous places like inside black holes and the surfaces of neutron stars? How about non-corporeal life which is neutrino-based (or something even more unlikely to interact with matter)?
Seems like they think they're the only ones, they're convinced of it, and they've "proven it" as far as they're concerned - but they certainly may well be mistaken in those beliefs.
Discussion on question by flox: How c…
Discussion on question by flox: How c…