Long day ahead. Perhaps time for discussion late tonight.
My pleasure.
If there be "one faith and one baptism" and "one fold and one shepherd" there must be one belief.
If the Church were only a spiritual entity and not a visible one there would be no outward signs for one to identify it as the one established by Christ.
Surely if a church is claiming to be the true one founded by Christ then it should be able to identify itself as such.
Looking at the New Testament as an historically reliable document we see that Jesus sent out particular men to go into the world and teach all things that he commanded them, if a church is claiming something contrary to the teachings of these men and their successors it can logically be identified as a false church.
It takes a process of elimination to find the true Church. Not to go into all the details but just to draw one example: A new church comes along and preaches that there is no Hell. I would line that up with the New Testament to see if that is what Jesus taught and I would eliminate this "church" from the possible ones Christ established