There are many people out there claiming to be teachers, so who do we believe? Who has Authority? Here are a few examples of doctrines on this:
1) THE HOLY SPIRIT & GOD'S WORD - Protestants, Evangelicals and Anabaptists often believe - That Jesus clearly told us the Holy Spirit will be sent as our teacher and comforter, who would lead us in all truth. The Holy Spirit is therefore our primary teacher, guide and source of authority, along with the Word of God, declared in scripture to be infallible. However the Holy Spirit dwells in millions of people, and the bible says some men have the specific ministry of teaching. Who you listen to is your responsibility. (I believe this) These are often in the Spirit believers.
2) GOD'S WORD & THE HUMAN MIND - Other Protestants, Evangelicals and Anabaptists often believe - that the Word of God is our authority, and that it is so clear that the sincere human mind can easily comprehend it, and that truth in the bible is self evident, and they do not therefore say things like "I believe the Holy Spirit has taught me.... this, or that." (I deny this teaching) Such people usually apply their brain power to such scriptures as "above all things do not swear an oath" and by brain power alone come to the conclusion it means "it is fine to swear oaths." Though the bible is often direct and clear, it is also written in symbols, parables and deals with things quote "hard to be understood", requiring help from God's Spirit.
3) THE POPE AND THE CATHOLIC CHURCH - Catholics say the Pope is infallible, and so is their church, a church with a long history of witch burning, so called heretic burning, massacres like Saint Bartholomew's Day Massacre, rules of just war, unjust wars of conquest, inquisitions, Crusades and the Conquistadores.
4) THE ORTHODOX CHURCH ONLY - The Orthodox deny their Titular Head of the Church is infallible, but say their church is infallible.
By saying this the Orthodox deny the Catholic church and the Popes are infallible, (because of the plethora of contradictions between their religions), and the Catholics believe the same in reverse about the Orthodox.