The Acts of the Apostles is poorly named because it is primarily the acts of only two apostles: Peter and Paul (and Paul is not actually considered to be an "apostle" by Luke, the author of Acts). Furthermore, it is Paul who emerges as the hero of the narrative, as well over half of Acts is devoted to his journeys and exploits. The portrait of Paul in Acts is striking for several reasons, not the least of which is the fact that letter writing, the activity for which Paul appears to have been known, is completely absent. In Acts Paul travels, preaches, heals, and escapes attempts on his life, but he doesn't write letters.
Dupertuis, R. (2009). Socratizing Paul: The portrait of Paul in acts. The Fourth R, 22(6), 11-18, 28.
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