"What?" the Doctor found himself saying, almost automatically, in response to the other man's question. His mind was a bit preoccupied with more important things, things such as the fact that he was standing opposite himself, and it was a self he'd never thought to see again. He should have thought of the possibility, he realized. The TARDIS had called numerous versions of the Doctor to her, so why not pull in the one Doctor who wasn't the Doctor at all? Why not pull in John Smith, poor, doomed John Smith, who wanted nothing more than a simple, human life?
"What?" the Doctor repeated, belatedly taking in what his human alter ego had said, and making a face at the idea that he was some sort of grim reaper come to remove John from the fabric of the universe. "What?! No! No, of course not! How would I ... What would I ... Why would I even want to?" The Doctor took a step back and ran a hand through his hair in one of his favorite nervous gestures. "I'm not here to replace you."