We will know for sure in heaven. There are plenty of passages in scripture that clearly say that Jesus Christ is the only Savior, and that His words are paramount to all other human beings before and after Him. I am quite convinced that Christ would never pass His own authority to Peter so that Peter and His colleagues could contradict Christ's Words. Therefore it is prudent to test all thoughts against the revealed Word of God.
Failures to put God's Word first have resulted in:
1. Augustine allegorizing the Book of Revelation. Allowing the enemy to turn the church from honoring the Word of God as the guide to understanding, to honoring the Traditions of Men. (Augustine set aside the millennial reign of Christ because he mistook Constantine's empire for Christ's reign. Also Augustine allegorizing the book of Revelation, and many Old Testament prophetic Books, into a books of fables which as we know from modern technology the events are totally plausible, as well as the fact that at no other time in history are the prophecies lined up completely for the end time scenario). Rapture, what is that?
2. On the Protestant side we have Martin Luther, who because the Jews were scattered into oblivion during his lifetime, he misrepresented God in regard to the Jews, and had antisemitic sentiments. (there are many passages that state that the Israelis will be regathered into the land in the last days. Viola, 1947 Israel is a nation, 1968 Jerusalem is Israel's capital.)
These failures to regard a straightforward reading of the scripture has resulted in the Crusades, the Inquisition, Antisemitism in the Church, a turning of believers eyes from the expectation of Christ's return at any moment and most importantly an erosion of believers trust in the studying and meditation on God's Word. Satan has been very busy working amongst God's people as the Bible has warned so many times.