And he gave the apostles, the prophets, the evangelists, the shepherds and teachers, to equip the saints for the work of ministry, for building up the body of Christ, until we all attain to the unity of the faith and of the knowledge of the Son of God, to mature manhood, to the measure of the stature of the fullness of Christ, so that we may no longer be children, tossed to and fro by the waves and carried about by every wind of doctrine, by human cunning, by craftiness in deceitful schemes.
In Ephesians 4:11–14, Paul explains to the church in Ephesus why God gave ministers and teachers to the church. God did this to equip the saints, to build up the body. What is His goal? The attainment of the unity of the faith and the knowledge of the Son of God. In other words, the goal is the spiritual maturity of believers. God gave ministers and teachers to the church in order to help the saints grow up.
This is necessary because until we grow up and become mature, we are are spiritually immature children, and the problem here is that those who are in this state are gullible and susceptible to false doctrine. Paul says that the spiritually immature are tossed to and fro by the waves and carried about by every wind of doctrine. They are inherently unstable. It's an interesting metaphor Paul uses because it's used elsewhere in Scripture to describe the nature of those who doubt (James 1:6) and the nature of false teachers (Jude 12–13). The false teachers are tossed about, and they cause others to experience the same instability.
The spiritually immature are those who are tossed around by human cunning, by craftiness in deceitful schemes. What does such cunning and craftiness look like? In 2 Corinthians 4:2, Paul uses this same language to describe those who "tamper with God's word." These are the false teachers that Paul had warned the Ephesian elders about when he said, "I know that after my departure fierce wolves will come in among you, not sparing the flock; and from among your own selves will arise men speaking twisted things, to draw away the disciples after them" (Acts 20:29–30).
The church is given faithful shepherds by God to guard the flock against such fierce wolves. Good shepherds can guard the flock from being carried about by every wind of doctrine only if they instruct the church in true doctrine. In other words, doctrine is not optional. If the flock isn't taught true doctrine by faithful pastors and teachers, they will be unstable and tossed around by the waves and the wind of false doctrine.
Christians who downplay the importance of doctrine, of good theology, are setting themselves and their churches up to be carried about by every wind of doctrine, to be spiritually immature and gullible. Our Lord calls us to something better. He calls us "to mature manhood, to the measure of the stature of the fullness of Christ, so that we may no longer be children."