Here are three Scriptural passages that have to be reconciled:
1) Jesus established a Church that he said "the gates of hell would not prevail against." (Matthew 16:17-19)
2) Jesus told us to take our disagreements to "the church." Logically, this must be the Church that He established. And it must be a visible, discernable, united Church. Christ wouldn't recommend that we settle disputes in an unidentifiable church. And He wouldn't recommend that we go to one of many churches with conflicting doctrines to settle doctrinal disputes, among other disputes. (Matthew 18:15-18)
3) The Church is the "pillar and foundation of truth." This reinforces the idea that Christ would not instruct us to settle disputes in churches that cannot agree on the truth; churches with competing doctrines.(1 Timothy 3:14-16)
Now only two churches have been around since Pentacost: the Catholic Church and the Orthodox Churches.