So here is a whimsical argument, perfect (though six days early) for the Feast of St. Thomas Aquinas:
This is where Michael Flynn’s Eifelheim is badly needed.
Augustine was pondering this stuff in the 5th century. Except his aliens lived on remote islands. Medieval piety baptized and even canonized dog-headed men. If you were rational and an animal, that was good enough for them.
Sometimes you hear skeptics say that the Church is terrified of what will happen to its provincial earth-bound gospel should we discover non-human intelligent life elsewhere in the universe. But the Church has always believed in non-human intelligent life. What else do you think angels are? All the discover of ET would show is that God has also made non-human corporeal life.
If we make first contact with the Vulcans on April 5, 2063 there will be a priest there soon after to see if they need the gospel. Of course, if the Vulcans are unfallen they won’t need it. And if they are fallen (which could be mighty difficult to tell depending on a host of factors) it may well be that our gospel is not salvific for them and God has something else in store for them.
If they are unfallen they will likely avoid us since what happens when our species meets a sinless race will be predicated entirely on power. If they are weaker than we, then the red man and the black man can tell you what we will do to them. If they are stronger, they might very well properly annihilate us in self defense.
C.S. Lewis speculates that the size of the universe may well be God’s quarantine to keep our infection from spreading. Seems reasonable to me.
But all that depends on them existing in the first places. At this point, we don’t even have a hint there is algae on other worlds, much less Vulcans.