Harmony in a normal physical body is not effected by external means, but is organic. The members may be many and diverse, but they are all necessary and have their respective places and work. So also with the body of Christ. Union with Christ is not dependent upon absolute uniformity except in the one thing--the fundamental experience by which we are made members of Christ. In the apostolic period the children of God who loved our Lord and were known of him were not all of one age or size or nationality. They had not all enjoyed the same social advantages, nor had they had the same intellectual attainments. The act of receiving Christ and his salvation did not perfect their knowledge; therefore they had to be patiently taught in order to bring them into the "unity of the faith." And for this purpose divinely chosen instructors were appointed, who must themselves "study" and give careful attention to "doctrine" (Eph. 4:11-14; 1 Tim. 3:13-16). But the gospel penetrates beneath the surface; it goes straight to the heart and reaches fundamental things. "There is neither Jew nor Greek; there is neither bond nor free, there is neither male nor female: _for ye are all one_ IN CHRIST JESUS" (Gal. 3:28). The unity of believers with Christ is, therefore, based on divine relationship, and _this is the fundamental basis of the true relationship of believers with each other_. In order to maintain spiritual relationship with Christ and his people, the Christian must have an obedient heart and "walk in the light of the Lord"; but we should always be ready to extend our fellowship to those whom Christ really receives and approves. How prone men have ever been to ignore this simple, divine standard and set up arbitrary rules of their own by which to measure others! This wrong tendency combined with the carnal ambitions of men who love to parade their own unscriptural ideas before the world and gain adherents has been the real cause of the disunion of Christians. But the Bible standard is what we are now considering. It teaches that the saved people were "members one of another" as well as members of Christ; that they were, in fact, "_all one in Christ Jesus_." [Sidenote: Unity a practical reality]