Paul’s admonition here is to not focus on these differences—Jew vs. Greek, bond vs. free, male vs. female—with regard to our inclusion in Christ. Rather, he said that we should focus on the reality of baptism, putting on Christ, living in Christ, etc. All of these categories were traditionally used to determine who was “in” and who was “out” of fellowship with God. No more! said Paul. In Christ fellowship with God is determined by fellowship with God.
Our oneness in Christ is a plural unity, or a unified plurality because Paul was speaking to the whole not to an individual. Thus, Christian unity is group thing as well as an individual thing. But it is not an individual group thing, either. Unity is necessarily tied to Set Theory and wholeness. While these ideas are abstract in their considerations, they have very practical and ordinary implications and applications that directly pertain to Christianity and Christ’s church.
In order to consider such implications and applications we need to think beyond what has passed for conventional Christian unity, the unity of various denominations. The effort to unify the various denominations falls far short of the mark for many reasons. First of all, the denominations themselves are structured to oppose unity in that they are defined by what sets them apart from other Christians. So, to try to unify what is by definition not in unity with Christ’s wholeness is fruitless. It starts on the wrong foot and barks up the wrong tree. Paul explicitly told us not to engage in subgroup structures like denominations.
“For when one says, ‘I follow Paul,’ and another, ‘I follow Apollos,’ are you not being merely human?” (1 Corinthians 3:4).
The goal of Christian unity is not simply to be in unity with other Christians or their churches, but to be in unity with Jesus Christ first and foremost. Christian unity is not in the churches, nor among various Christians. Christian unity is not built or achieved by us. Rather, it is given by God, and has already been given in Christ. It is not a long hoped for ideal to aspire toward, it is a living reality. It does not depend on church pronouncements or corporate documents. It depends upon God in Christ.
– from Galatians–Backstory / Christstory (coming Dec. 2015)