Personally, with billions of stars and untold number of planets and solar systems out there in the universe, I would find it nearly impossible not to think there isn’t life out there.
I don’t think that makes me a lunatic, I’m just playing the numbers game here.
If there really are aliens, I find it hard to believe they would not have tried to conquer us or exterminate us. The human race is a dangerous bunch.
We’re almost certainly alone. If you want to play a numbers game this is the link to do it with, it’s a Drake’s Equation calculator.
None of the values in Drake’s Equation is actually known, so there are no wrong inputs. But trying to input reasonable numbers I come out with less then ten alien civilizations. Then stir in factors Drake didn’t consider, such as the density of stars in a given area of space (higher density areas being more subject to radiation, gas, and gravity interference with each other, remember we are out in the galactic sticks ) and I conclude it’s lucky we ourselves are here at all, much less competitors.
http://www.seti.org/site/pp.asp?c=ktJ2J9MMIsE&b=179074