The closest star. But, we struggle to observe it in any capacity. Indeed, only today we did. And that's nothing to say of the next closest star, or the next, or the next, ad (nearly) infinitum.
If planets in this zone aren't as rare as we think, life in the universe might also not be as rare as we think.
To me, the question is more "where," rather than "if."
Something that's probably a lot more rare is favorable conditions over a long time period. It took a long time for life on planet earth to evolve into more complex forms.
I'm pretty sure we're not the only ones out there. But will mankind and our space neighbours exist long enough to facilitate communication?
Is every species that is competitive enough to subdue all other life on its planet doomed to disintegrate due to internal conflict?
We don't know how difficult it is to create life. The universe is big, but the difficulty of creating life might be much bigger.
Thus. It is not certain that there is life elsewhere.