As I have studied the Book of Acts this summer I have noticed three motifs that seem to weave together throughout:
Pneumatology:
Obviously the Holy Spirit is an important character in the Book of Acts. The Spirit is given to many Jews on the Day of Pentecost in 2.1-4. The Spirit refills the fearful Christians in 4.31. The Spirit comes upon Samaritans in 8.17. The Spirit comes upon Gentiles in 10.44. The Spirit comes about disciples who had been baptized by John the Baptist in 19.6. The narrative of the book functions under the presupposition that the Spirit is guiding the church.
Catholicity:
The Spirit’s work has to do with bringing different people into one church. The Jews, Samaritans, and Gentiles all receive the same Spirit. This makes them equals in the community of Messiah. As the Apostle Peter says in 10.34, “I most certainly understand now that God is not one to show partiality” and in 15.9, “[God] made no distinction between us and them” signifying that all are equal “in Christ.”
This equality creates a sense of “catholicity” or oneness. I have argued that this is part of the motivation for the inclusion of the story in 19.1-7: all Christians are one so they should share the baptism unto Christ. The baptism unto John is insufficient for Christians. In Acts there is the positive argument saying “welcome” to one and to all and there is the negative argument saying that alternative or fringe expressions of Christianity should follow the Spirit’s lead toward unity with the “mainstream” church.
Apostolic Authority:
The “mainstream” church is the one that connects to the apostles. When Samaritans or Gentiles (as a group) are shown to be equal with the Jews and welcomed into the church it is at the hands of Peter (and John in Acts 8). When the disciples who were baptized unto John integrate it is through the work of Paul in 19.1-7. When major decisions are made such as whether or not Gentiles must be circumcised it is the testimony and ruling of apostolic leaders like Paul, Barnabas, Peter, and James that signifies the direction that the Spirit aims to take the church.
What do you think of the function of these three motifs and their inter-relatedness in the Book of Acts?
the archives near Emmaus 
Never really noticed them ..
Was the Christian church the “mainstream” or was the Jewish Synagogue the “mainstream” at the time? To me it certainly seems that the disciples and early believers where the fringe going against the mainstream, especially this the Jewish Rabbis maintained a stance of superiority, interrogating and punishing at they saw fit.
Roland
I should clarify that I mean Luke’s idea of “mainstream,” i.e. the church connected to the apostles.