Psacramento, at the line where proof and evidence ceases, that's where faith begins. The Bible describes faith in terms of believing the unseen, and says it takes a special person to have the kind of faith that pleases God.
If there were solid factual evidence (such as the Catholics looked for in the relics like the Shroud of Turin) for every item of faith, faith would no longer be necessary because the religions would be teaching only facts. But they cannot, because religions deal in the realm of the unseeable and unknowable -- and even in the historically unverifiable.
It takes faith (and I'm not demeaning anyone who has faith, I'm just stating what my Christian girlfriend tells me) -- and that's what makes religion including Christianity what it is.