'Are we alone in the cosmos? If yes, we can never be sure. If no, we might well have an answer within the decade. The 22 authors of these fascinating and informative essays say no, we are not alone, despite the fact that so far not a shred of evidence has been found for the existence of life elsewhere in the universe. But just in case they are right, we need to start thinking about the possibility that we are not alone, and here is a good place to start.' Owen Gingerich, Harvard-Smithsonian Center for Astrophysics and author of God's Planet