I sincerely believe that the Earth is rare. I even dare say it is unique, just like how every human being is unique. Earth is truly one of a kind, and that is why I love it so much. Now by saying that Earth is unique does not mean that there won't be other worlds like it. Thus there could be countless 'earth-like' worlds out there, but only some would have Life. And among those that are life-bearing, possibly only a fraction would be intelligent and sentient.
There is no debate in the argument of the Rare Earth hypothesis that the emergence of complex multicellular life on Earth required an improbable combination of astrophysical and geological events and circumstances. Other than that, it cannot have bearing on how common life is on other parts of the universe.
I appreciate the fact that the "Rare Earth Hypothesis" was aptly named - which simply means that the Earth is rare, which I rather consider the same as saying that diamonds are rare.
The Earth is precious and unique. There is no place like home.
