You can't never say yes. It will definitely a "no" when we find clear evidence of intelligent life elsewhere, but we should know for sure when we inspect every

You can't never say yes. It will definitely a "no" when we find clear evidence of intelligent life elsewhere, but we should know for sure when we inspect every other place in the universe, in all history of it, and that is billions of light years spanning billions of years to say "yes". And we can't even rule that out even in our closest star system, at just 4 light years from here, yet. Everything is too far away from our view to rule out that is not in some place that we didn't see yet, because practically everything fits in that definition.