Aliens... that's what this post is about. Particularly, do aliens exist or not? "Ontology" isn't quite the right word for this, but "Extraterrestrial Ontology" sounds really cool, so I'm using it.
So there are two issues I was thinking about. First, is it possible that aliens actually exist? Second, why are people so interested in aliens and trying to find them?
I'm not going to say that it's absolutely impossible that aliens might exist. But I am pretty convinced they don't, and I think there's a good case for that from the Bible.
First, the biblical account of creation says nothing about God creating life on another planet, which seems to imply that He did not. Also, the earth was created first, while the Sun, Moon, and Stars (and probably galaxies, and everything else in space) where created after earth. Again, the implication is that the focus of creation is the earth and its inhabitants. Genesis gives a detailed account of the creation of Man (on earth), but says nothing about extraterrestrial life forms.
Second, if aliens do exist, are they saved? Do they have original sin, or are they sinless? The Bible says that all sinned in Adam. For as in Adam all die, so also in Christ all shall be made alive. (1 Corinthians 15:22). Adam represented all of the human race, but did he represent aliens too? If he did, did Jesus go to their planet(s) and die for them too? This would definitely be heresy... If the Church is the bride of Christ, and there are two or more Churches on different planets, would Jesus would be a polygamist? Not good...
The absence of any mention of aliens in the creation account, and the fact that Jesus came and died and was resurrected on this earth for the human race are enough reasons, in my opinion, to say the aliens do not exist. Bigfoot though... that's another story.
So why do people try so hard to find aliens? Most of the exploration done by NASA and research by other organizations has focused (and spent lots of money) for the express purpose of finding extraterrestrial life. According to evolutionary theory there is no reason why life couldn't have evolved in other planets, in the same way is supposedly did on ours. Many evolutionists believe that aliens have been "evolving" much longer than we have, and they may even be responsible for life on earth.
In the movie Expelled: No Intelligence Allowed there are many interviews with prominent evolutionists. Richard Dawkins speaks in a number of interviews throughout the movie, and he's always saying the Intelligent Design is a completely "unscientific" theory. But in the final interview, Ben Stein asks what he thinks about the possibility of aliens being the reason we have life here on earth. Dawkins supports this idea! Without even realizing it he shows his true colors, that he's not worried about what is supposedly "scientific" or not. If aliens brought life to earth that's intelligent design, it's just doesn't involve God (Dawkins doesn't tell us where the aliens came from...). And this, I think this the real reason most people are so interested in finding aliens. They think finding aliens would prove evolution is true, and that that would free them from God's authority as creator.
Here's one of the clips where Stein is interviewing Dawkins. He talks about aliens towards the end.
As far as all the stories about "abductions" and UFO's etc. most of those have been proved to be hoaxes. There's a really good book I had (I think Scott Cone lost it...) called Alien Intrusion by Gary Bates. http://www.amazon.com/Alien-Intrusion-Gary-Bates/dp/0890514356
He does a good job of debunking the most popular alien hoaxes, and then looks at actual seemingly paranormal activity that does occur, but from a Christian viewpoint. If you want to know more about it, you'll have to read the book.