The study of soul predates Christianity.
While the soul cannot be reached through the scientific method it's reached through philosophy and is a philosophical subject of study. I think the only "leap of faith" is the soul is immortal or not. If you think the word soul is too much religious you can use the word software. The word soul was originated outside religion.
It can be reached through intuition too. Search your own intuition and you will see.
Short answer, he doesn't have any objective and verifiable evidence. It's all based on how you feel about it.