That is, nevertheless the essence of his argument.
...and that's good enough for me. He points out that the Milky Way is only 100,000 ly wide. Therefore, if there were alien life out there with advanced civilizations, they would find travelling such a small distance a piece of cake and would have discovered us by now. But they haven't. And Tegmark says if the whole galaxy we live in has no life, it's highly unlikely there's life any elsewhere, either -- even if the universe is infinite, it's likely we're the only living creatures in it.
Jesus, I think I know you. Is there a Libby in your past? Did Felix fly around your kitchen? If so, it's me, Green Lantern. Directly reachable at tothrowaway at gmail.