Does it matter whether the aliens have visited earth, or only that life exists elsewhere in the universe?

Do they need to be intelligent aliens, by some definition of intelligent?

And do they have to still exist today, or is it enough to think life may gave existed elsewhere at some point?

2. Do I believe other intelligent life forms visit earth in their flying saucers, abduct people, anal probe them, abduct and slaughter cows, build pyramids, and - apparently - crash often? No, not really. I mean, I can't rule it out, but my personal subjective Bayesian prior towards this notion would probably be something like 0.001 or so. But that's actually up from years past, as we learn more about more possibly inhabitable planets that are closer to Earth than was previously known, etc.