The Christian needs to hold on to that Christ himself sets the terms for the legitimacy of Bible teachers.
First, they are chosen by and ordained by his church as an organized body of believers through history (Acts 6:3)
If they are not from the church they are not from Christ because he chooses to sanctify the world through the church that he calls to himself (1 John 2:19).
Second, their training and approval is by the church of which all Christians of goodwill and faithful understanding are members (Acts 15:22).
Secular psychologists, doctors, lawyers, philosophers or theologians (even those that recognize the importance and value of the Bible in the history of western civilization and the formation of the modern mind) are not thereby approved to teach it.
The Bible is not everyone’s book; it is the book written by and for the church.
It is for the world in the practical sense but delivered by and through the church (Romans 10:14-15)
“Ministries” and corporations that organize themselves to teach the church are often hubs of bad doctrine, immorality and scandal. Many are businesses run by people that otherwise could never be ordained by a church, so they start an organization that isn’t subject to the regulations, rules and historical judgements of the church in history.
It’s easy to gather a group of Biblically uneducated followers; every cult does it.
Here, the Christian needs to be seriously and responsibly concerned about outside sources (even if claiming faith) posturing to “teach” the church.
1st, the teaching is almost always bad.
2nd, the church is designed by God to teach you.
3rd, this tends to be how false doctrines and dogmas get started.
4th, their muddled theories however much they intrigue your intellect will never increase the well being of your spirit.
The world cannot teach the church the true meaning of the Bible because it is spiritually discerned and only spiritually reborn people can understand it.
And those that are spiritually reborn will understand what the will of God is in these important matters.
From 1 Corinthians chapter 1
17 For Christ did not send me to baptize but to preach the gospel, and not with words of eloquent wisdom, lest the cross of Christ be emptied of its power.
18 For the word of the cross is folly to those who are perishing, but to us who are being saved it is the power of God.19 For it is written,
“I will destroy the wisdom of the wise,
and the discernment of the discerning I will thwart.”
20 Where is the one who is wise? Where is the scribe? Where is the debater of this age? Has not God made foolish the wisdom of the world?21 For since, in the wisdom of God, the world did not know God through wisdom, it pleased God through the folly of what we preach[b] to save those who believe. 22 For Jews demand signs and Greeks seek wisdom, 23 but we preach Christ crucified, a stumbling block to Jews and folly to Gentiles, 24 but to those who are called, both Jews and Greeks, Christ the power of God and the wisdom of God. 25 For the foolishness of God is wiser than men, and the weakness of God is stronger than men.
26 For consider your calling, brothers: not many of you were wise according to worldly standards,[c] not many were powerful, not many were of noble birth. 27 But God chose what is foolish in the world to shame the wise; God chose what is weak in the world to shame the strong; 28 God chose what is low and despised in the world, even things that are not, to bring to nothing things that are, 29 so that no human being[d] might boast in the presence of God. 30 And because of him[e] you are in Christ Jesus, who became to us wisdom from God, righteousness and sanctification and redemption, 31 so that, as it is written, “Let the one who boasts, boast in the Lord.”
Christian Theology 