It's one of those questions that we probably won't ever know the answer to, much like: How long is it going to take people to actually proofread their titles when they post in General Discussion?
If I were him and he was me then I can't become him, so I'd have to be me or someone else beforehand. And if he thought he was him when he was me then I would think that I was him, but I think I am me so I can't be him. I have to be me.