In my reading of the scholarly literature, there are four major theories that attempt to account for the “we” passages in the book of Acts, but let me know if there are other options that I have not considered.
- The instances where the “we” appears in the latter half of Acts signal that the author was an eyewitness and firsthand participant in the events that were narrated. The arguments in favour of Lukan authorship, as noted by Irenaeus, are that 2 Timothy 4:11 claims that only Luke remained with Paul when he was imprisoned in Rome and Luke is not named in the book of Acts in keeping with the anonymity of the book. However, it is also possible that the book was written by another co-worker of Paul.
- The presence of the “we” in Acts was a residue on the author’s use of an earlier source or a travel diary from one of Paul’s co-workers. Since the “we” sections seems consistent with the literary style of the rest of the narrative, it may seem surprising that the author would not just change the first-person in the source to the third-person when editing it, but perhaps the author retained the “we” to signal the use of an eyewitness source. There is debate about the extent to which this hypothetical source can be reconstructed.
- The inclusion of the “we” in Acts reflects some sort of dramatic literary device. Vernon Robbins has put forward the argument that the first-person plural was conventional in narratives of ancient sea voyages here. Alternatively, the narrator becomes a character in the story through the use of “we” or the “we” puts the reader in the middle of the dramatic action.
- The book of Acts uses the “we” to advance a “pseudonymous” or a fictional claim that it was written by an eyewitness of Paul’s missionary activities and thus provides verisimilitude for the events that were recorded.
The Jesus Memoirs 