Writing from a purely secular perspective here, astrophysicist Ethan Siegel argues that we may well be alone in the cosmos.
There may never have been another intelligent, technologically advanced alien species in the entire history of the Universe. Last week, in the New York Times, scientist Adam Frank emphatically wrote that Yes, There Have Been Aliens, concluding that given all the potentially habitable worlds we know must be out there from our astrophysical discoveries, intelligent life must have arisen. What he fails to account for, however, is the magnitude of the unknowns that abiogenesis, evolution, long-term habitability and other factors bring into the equation. Although it’s true that there are an astronomical number of possibilities for intelligent, technologically advanced lifeforms, the huge uncertainties make it a very real possibility that humans are the only spacefaring aliens our Universe has ever known.
I agree with him for theological reasons. I've written before on this subject - i.e., here and here.