I just had this thought that, say, in prison, or a bad relationship, there could be a person in the room right next to yours, and there could be such a gulf between you that you are in fact completely and utterly alone.

... If there's no communication between you, what else would you call that but "alone"?

Edit: I should say that I think I hear what you're saying, and I further think that there's always hope that you could bridge that gap.