I in them and you in me, that they may become perfectly one, so that the world may know that you sent me and loved them even as you loved me (ESV).
It seems some Evangelicals have found a verse to use as a key: John 17.23. They believe that if Christians work for unity (in all cases, I observe only external tactics to achieve this “unity”), then, the numbers will come. But is this what Jesus was talking about when He prayed to his Father? According to both the text and history, Jesus was not speaking of outward unity, such as various gatherings and media events.
The text is clear that Jesus would be in us as Christians. This is unseen unity, however, and distinctly different than for what is being clamored. Additionally, historic truth can help us discern how we are to take John 17.23.
Jesus’ disciples were a diverse lot. Judas Iscariot was probably a Pharisee like his father Simon. Matthew was a tax collector who would have had to gain his concession through dealings with the priests and officials of Roman Judea. Simon the Zealot’s doctrine included revolution against Rome. From what we know of Peter, Andrew, James, and John, they were fishers following their immediate ancestors. After Jesus’ resurrection was the gospel method unbridled external unity? No, it was not.
During the days of His flesh, Jesus taught His disciples and formed their understanding of ministry. After His ascension, the book of Acts records some of their ministries along with that of Paul’s. What we don’t find is a push for external unity. I mean, if John 17.23 is speaking of some kind of mechanistic effect that would bring the world to Christ by seeing the external unity of Christians, then where is the evidence in N. T. writings?