Thanks, but the point is that it is impossible to speak to a set. The Church of which Christ speaks in Matt 18:17 is not a set; it is a hierarchical institution. That is why one can "tell it to the Church", because one is telling it to the bishops or presbyters in the Church. And when Jesus says in Matt 16:18 that He will build His Church, He is not saying "I will add to the set of all believers"; He is talking about the hierarchical institution "built upon the foundation of the apostles and prophets." (Eph 2:20)
-A8