It is impossible for satan to defeat the church from the outside, as long as all the members remain faithful. The way for him to gain a victory is to gather supporters within the church who will work in secret to betray the members. For this reason, order and discipline are imperative for a church, that those who are a leaven may not be tolerated in it. This includes those who again conform to this world, who walk carnally, who seek their own, who are enemies of the cross of Christ. Those that are such, have also become betrayers to the truth.
Unity, or oneness, of the Spirit occurs in all who are truly of the Spirit of Christ. There are diversities of gifts within the body, but strife and discord arise only from diverse spirits. It is necessary to recognize the true Spirit and discern the strange spirits so that we do not allow these diverse and strange spirits into the church.
--Excerpt: S.H. Froehlich