We would be very arrogant to think that there is life only on this planet we call earth. There is a good chance that there are other life forms "out there" and we might not be able to even recognize them as life forms. I doubt all life forms are carbon based. Can't even fathom the "Multiverse" theories or other possible dimensions. In reality we know nothing of this place we are.
Very heady subject...
"Human beings seldom think for themselves... For the most part, members of our species simply repeat what they are told and become upset if they are exposed to any different view. The characteristic human trait is not awareness but conformity... We are stubborn, self-destructive conformists. Any other view of our species is just a self-congratulatory delusion."