Do us both a favor and don't argue with me about it.
Yeah, yeah, no.
Since Brock put the argument best, I will quote him:
Based on the estimated size of the universe, and the statistical odds of all the necessary events happening on a given suitable planet to produce life, I think it likely there is some other form of advanced life somewhere in the vastness of the universe, though whether or not it is anywhere near close enough for us to discover anytime soon is debatable.
I think that the ability to calculate the statistical odds are a bit daunting.
I'm trying to remember the name of the famed atheist who once debated C. S. Lewis. He was an Oxford scholar who believed that there was insufficient evidence for the existence of God. When the Human Genome Project published its findings, he--wait, I know where to find it. I mentioned him some years ago when I wrote Faith and Gaming: Teleology. His name is Antony Flew, and at 81 years old he became a deist after having been perhaps the world's foremost living atheist. He did so because he said he realized that the basic building blocks of life could not have happened by "any combination of chance and the known laws of science".
If Flew is correct, then the probability of life occurring anywhere in the universe, including here, is zero. In that case, it must have appeared here based on something other than chance; and if that is so, no argument from probability can establish that it might have occurred more than once, since it is against all probability for it to have occurred even once.
Now, I'm not so arrogant as to say that I am certain there's no life anywhere else in the universe. All I will say is I consider it highly improbable, yet just as I also consider it highly improbable that we will ever travel through time I have put my mind at times to the problems inherent in the ramifications of the possibility. That is, I have given some thought to what it would mean for there to be "intelligent aliens" out there.
I've got an article somewhere about that, but it's not been published and I don't see it appearing any time soon; I also don't see the point in copying it to the forum.
Now, what I said was
I really believe that there are not a vast number of divergent dimensions more or less like our own in which anything is possible. I say so in the book. It's just fun to contemplate as a game.
I do not consider it arrogant to have made that statement, any more than I consider it arrogant for me to say that I really believe that Wawa has the best price on half and half in our area, and Rite Aid has the best price on whole milk. I have made some investigations and reached a conclusion. The evidence is adequate for me. I certainly did not say that you would be stupid or arrogant to believe otherwise; I can see that you might find some of the evidence of additional dimensions compelling (although the suggestion that there are dimensions we cannot perceive that are part of this universe is a far cry from stating that there are entire universes unknown to us). I personally believe that other universes do not exist, or that if they do they are so completely unlike ours that they are rather irrelevant to any discussions we might have.
--M. J. Young