I would like to recommend a wonderful book, "The Privileged Planet" by Guillermo Gonzalez and Jay W. Richards. I recently saw the TV documentary based on it and was deeply impressed. The main thesis is fascinating: that the Earth is situated in a "galactic habitable zone," an area of the universe that is protected from the deadliest cosmic dangers. They provide an endless array of mathematically improbable, but favorable factors that allows Earth to support complex life. It would appear that advanced life may be much, much more rare than has been suggested by Carl Sagan, et al.
Earth is also in a unique position in the galaxy to allow a clear view of the heavens so mankind can study and discover its secrets. Not only are there no cosmic dust or gas clouds surrounding us, we have been given an unusually transparent atmosphere, a rare thing in itself.
This was a new idea to me. I had always taken for granted that other star systems would be just as good a vantage point for observation of the rest of the universe. Not until you see the documentary do you realize how strange and mysterious (and lucky) our planet's location is.
It's difficult to argue chance causation under these circumstances. The confluence of so many mathematical improbabilities is serendipitous, to say the last.
Thanks for the excellent post, Liberty Wins, and for the book recommendation! "The Privileged Planet" sounds fascinating.