The Vatican's official astronomer, Brother Guy Consolmagno, has given an interview in which he discusses the Vatican's thinking on what to do if alien intelligence is discovered.
We find an intelligent civilization and there's no way in creation we can communicate with them because they're so alien to us. We can't talk to dolphins now. In which case, we'll never know.

Second scenario: We find the intelligent civilization. We can communicate. We discover that they have the two essentials that theologians talk about for the human soul, intelligence and free will. They know who they are, they're self-aware, and they're able to do something about it. I think dogs are self-aware, but they don't have a whole lot of free will. Maybe computers are the same sort of thing. Human beings have to have both...

A third scenario: We find a dozen civilizations out there, and a bunch of Jehovah's witnesses go up and convert them all. At the end of the day, every civilization is Christian, except the human race is still not too sure about this. I mean, anything's possible.

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