Aliens
Of course, some people would say that the Fermi Paradox isn't a paradox at all and I would tend to agree. First of all, it makes the assumption that (intelligent) life should be abundant in the universe, eh, why? And the rarity of intelligent life is perhaps the simplest solution to the Fermi Paradox.
Take for example what I said to Feuds, for simplicity's sake, imagine it was just us and one other advanced civilisation in the entire universe. Clearly the alien civilisation would be wrong to conclude that no other advanced civilisation exists because they haven't detected any (or us in this case (us being the extraterrestrials from their POV))
And then some people say - but haven't we been emitting radio signals for over a century? Yeah, so. They're still limited to the speed of light and while technically infinite are also subject to the inverse square law, so an advanced civilisation even in our immediate galactic neighbourhood would need some pretty fancy-schmancy gear to detect them.
So I think that the answer, as are so many to the big questions in science, is that it's unknown.
Feuds I think is a Christian (much to the chagrin of Tiger

) and it's been a bit of a mixed bag so far from the Christians but I'd like to know that if you don't believe aliens exist (forget UFOs for a second) then why not, is it purely a religious belief?