Humans contain a lot of things that us Guides do not. We're the only ones who matter here. You seem like a smart enough person, so I'll ask you this instead: what do you think we're missing? It's really only one specific thing. Humans are very special.

[ A small smile, perhaps, is what he'll allow himself. ]

... Either way, that has always been what we used to determine who "stays". It seems the most fitting, doesn't it? You've all seen so many Hearts, after all. If you think that's you, you have every right to argue that case.