When our first parents Adam and Eve disobeyed God in the Garden of Eden they did more than just separate themselves from God, they separated from each other. The history of the world has been the war of the world; how could it be otherwise? When man turned away from God who is light (understanding), and love, he turned to the darkness and every form of selfish evil.
“No longer live as the Gentiles do, in the futility of their minds; darkened in understanding, alienated from the life of God because of their ignorance, because of their hardness of heart, they have become callous and have handed themselves over to licentiousness for the practice of every kind of impurity to excess.” Ephesians 4:17-19
The apostle’s remedy for a divided people is two-fold, first, Christ must dwell in one’s heart through faith, and apart from such a living reality, all attempts at “godliness” will be futile because as we have seen Christ is at the center of God’s plan for man, and the only means for God to receive glory.
“For this reason I kneel before the Father …that Christ may dwell in your hearts through faith” Ephesians 3:14&17.
Second, the Christian must grow up in Christ and receive the truth (sound doctrine), so that he may live the truth in love. All sin is falsehood, lies, deceitfulness, and scheming, and that includes all man made religions.
“So that we may no longer be infants, tossed by waves and swept along by every wind of teaching arising from human trickery, from their cunning in the interests of deceitful scheming. Rather, living the truth in love” Ephesians 4:15-15
Only when the church is united in the same doctrine is it truly united!