Believing that there are civilizations and life around other worlds is belief. I don't think that it will be simple to even recognize "life" on another world, let alone "intelligence" or "civilization." We can barely define these for ourselves. For example, our DNA is composed to a large degree of bases that were taken from viruses that invaded our genome over millions and millions of years. Some of that material has adapted to create our character as intelligent beings -- so that DNA which randomly entered our genome is crucial to defining us, and it is ours by accident. How would such a process go on on another world? We don't even know if life necessarily has to be based on DNA or not. And honestly civilization does not seem to me to have been inevitable, considering that a recent study suggests that humans were reduced to a very small number of individuals at different times in our history. And technology and scientific discovery and progress are also not inevitable (try Richard Rhodes' The Making of the Atom Bomb for a great example). So what could be out there? Could we even see it? And is it possible that beings somewhat like Earth's would even overlap in time? There are lots of worlds, and I myself like to believe the others are out there, but it's just a belief.