In your worldview if one has a different understanding even on eternal matters of truth as in matters of faith and/or doctrine then they are the ones who must be wrong. That makes YOU the ultimate authority, the pillar and bulwark of the truth if you will.
1. The word of God is the authority but you rob the authority with your tradition don't you? Matt:15:6
About comment #1
First, the Word of God is not wholly contained in Scripture (John 21:25).
Unless the Church is visible, somewhere to go to settle issues between the called out separated ones then the collection of called out separated ones cannot determine with authority what is true in such a matter as to settle the issue. Without an authoritative Church, the Church is useless in settling issues making Jesus' directives moot in Mat 18:15-18 and Paul's description of the Church as useless in 1 Tim 3:15.
your spirit is dead.