He doesn't understand how you can just stop being human. Unless maybe it was something like lycanthropy. Even then, the infected were still human, they were just something else too. It doesn't make sense to him, but he doesn't ask about it again, instead preferring to puzzle it out on his own.

He's also never heard of a spell that turns ghosts corporeal, so that's where he redirects his attention for the moment. He's surprised Lambert calls it 'simple.' Then again, with how different magic was between worlds, should he really be surprised.

"How can magic be so different in so many places?"