Read my OP: MT. 23:9, "And you are not to be called teacher for you have ONE teacher and that's Christ."
1 Corinthians 3:3-9, "You are still worldly. For since there is jealousy and quarreling among you, are you not worldly? For when one says; "I folow Paul', and another, "I follow Apollos," are you not mere men? What, after all is Apollos? And what is Paul? Only servants through whom you came to believe." Read the rest of that verse to see that only God makes things grow.
Isaiah 2:22 "Stop trusting in man who has but a breath in his nostrils. Of what account is he?"
Psalm 146:3 "Do not put your trust in princes, in mortal men who cannot save. When their spirit departs, they return to the ground. On that very day their plans come to nothing."
Psalm 49:13, "This is the fate of those who trust in themselves, and of their followers who approve of their sayings. Like sheep they are destined for the grave, and death will feed on them."
The whole bible tells us that the infallible truth comes from God's word alone. The words of humans die when humans die; only God's Word lasts forever.
So as Paul explains, what causes divisions among people is when people want to follow humans, like Luther, Calvin, the pope, etc, not God. And as I explained in my OP, that's why there are so many different denominations and contradictory teachings in Christianity. But the sinful nature is always at work inside a Christian as Paul knew it would be. So people continue to ignore Paul and keep listening to theologians, pastors, and Christian writers. So the Christian church is more divided than ever before because of that.
But if one doesn't trust God's word alone, then he can't spot a false teacher if he stood right in front of him.