The simplest answer--by far--is that Peter & Paul were still living when Acts was written. These two men (arguably along with James the Lord's brother) are the main characters of the book of Acts, and Acts traces the history of Christianity through their experiences.
The narrative in Acts ends in AD 62. All 3 men (Peter, Paul, James) died within 6 years of this time, yet you would never know this from reading Acts. Their deaths, and the persecution of the Christians that came in the latter part of Nero's reign, are highly relevant to the material presented in Acts. In fact, James' murder by a Sanhedrin-motivated lynch mob during a Roman interregnum would precisely illustrate the argument the author is trying to make about persecution of the Christians.
Why does the author of Acts exclude such highly relevant information from this account? Because these events hadn't happened yet.
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In the appendices I will present evidence in favor of this view, and review several competing views.
Appendix 1 - Evidences Acts was written in AD 62
Volumes could be written on each of these topics--I'll quickly highlight 7 major arguments that Acts brings the story up to the present time as of its publication:
- No mention of the destruction of the temple (occurred AD 70) which, had it already happened, would have decisively demonstrated the argument the author develops through Stephen's lengthy sermon in chapter 7, and validated the Olivet Discourse in Luke 21.
- The relationship between Christianity & Rome presented in & presupposed by the narrative only works prior to the Neronian persecution of Christians (began AD 64 or 65). In Luke-Acts the Romans are presented in a remarkably positive light, and are characterized as reasonably just & impartial towards Christians. It would be folly to pretend this were the case after Nero started burning Christians alive.
- The relationship between Christianity & Judaism presented in & presupposed by the narrative only works prior to the Great Revolt (began AD 66). The author is trying to claim that Christianity is protected as a legal religion under Roman law because it is a legitimate practice of Judaism--the Jewish origin & nature of Christianity is painstakingly outlined in Luke-Acts. This is a sensible argument to make prior to 66; it is suicidal to do so once the center of Judaism has engaged in full-scale, open rebellion against Rome. (hey Rome, you know that group that just started a war with Rome, yeah, we're part of them)
- The focus of the last third of Acts is setting the stage for Paul's trial before Caesar, but neither the trial nor the outcome are recounted
- Acts is written within a legal framework. There are 16 trials recorded in Acts, and an abundance of Roman (and Jewish) legal precedents are cited. Acts would make sense as a document written to defend Paul before Caesar. If Acts were written at a later date, such a legal history would be non-sensical if it did not cite the legal precedent from the court of last resort (the trial before Caesar).
- All 3 of the main characters of Acts are dead within 6 years of the end of the narrative, and their deaths occur under circumstances highly relevant to the themes & arguments of the book of Acts
- The argument developed at length by Colin Hemer (source), that the imminence of the last few chapters of Acts speaks to an author recounting events that have just happened.
Appendix 2 - Arguments from Silence
Are points 1, 4, and 6 arguments from silence, and therefore fallacious?
An argument from silence is not fallacious if the following 3 conditions are met:
- The information would be known to the author
- The information would be interesting to the author
- The information would be relevant to the point the author is making
Arguments 1, 4, and 6 pass all three tests.
Appendix 3 - Competing Views
Other explanations given for excluding Peter & Paul's deaths from Acts include:
- The audience already knew this information so there's no need to mention it. The audience may well have already known a great deal of what is recorded in Acts, but this would be akin to ending the Gospels when Jesus is delivered to Pilate. Luke & Acts are introduced by prologues, and the author acknowledges the reader already knows some of this information, but he's writing to ensure an accurate account is given of important matters. Peter & Paul's deaths as martyrs are important matters (i.e. consider how it is discussed in literature shortly thereafter, such as 1 Clement 5).
- The purpose of Acts was to show how Christianity arrived in Rome - now that Paul has arrived this has been accomplished. This is not the case - Christianity arrived in Rome well before Paul. We know this not only from historians (e.g. Justin, Clement of Alexandria, Eusebius, Jerome, etc.) but also from Paul's own epistle to the Romans. Paul wrote an epistle to Rome ~3 years before he himself arrived there, and there was already a Christian community there to write to.
- The author intended a third volume after Luke & Acts, and this would have been part of the third volume. While this is possible, it is also ad-hoc. And because we have the Gospel of Luke, we know the style of the author in telling a story: he gives the setting, identifies the main characters, recounts their key events, gives foreshadowing, builds tension and then...resolves it! The Gospel of Luke follows this arc; Acts does as well except for resolving the tension at the end. Even if the author had planned a 3rd volume, it would be inconsistent with his style to leave the tension he has developed around Paul's trial unresolved...unless of course the trial hadn't happened yet. Thus, even if the author had intended a 3rd account at some point, it still leaves the publication of Acts in the year 62, prior to Peter & Paul's deaths.
Appendix 4 - Late Dates for Acts?
The OP asks why some scholars date the book of Acts much later. There are 4 principal reasons.
Luke was written before Acts, and Luke includes details about the Roman Jewish War that couldn't have been known in advance, therefore Luke was written after the Roman Jewish War (occurred AD 66-73). This is circular. One cannot objectively evaluate a book about prophecy by starting with the a priori assumption that all prophecy is fake--to do so would be to decide on the very variable under consideration before even looking at the evidence (not very scientific!). To argue that the prophecy in Luke could not be real because prophecy is not real is but circular reasoning. A more detailed discussion can be found in my post here.
The Synoptic Problem. Many scholars believe Mark was the first of the Synoptic Gospels written (this is known as Markan Priority), and Luke used Mark as a source. If Mark was written ~AD 70, then Luke was written some years after that. Markan Priority as a theory has some serious difficulties, and the belief that Mark was written circa AD 70 is based almost entirely on the fact that it propheies of the Roman Jewish War--the argument is just as circular when applied to Mark as it is when applied to Luke (see #1).
This is what they were taught. An academic can only afford to challenge the consensus on a few matters if they wish to stay employed. Because 19th century scholars assumed late dates for the composition of most of the New Testament (more on that below), many textbooks continue to repeat late dates preferred by prior generations of scholars rather than revisit the evidence itself.
A desire to discredit the Gospel accounts. Those who wish to dismiss the Gospel narratives as fiction have long engaged in a form of naturalistic, circular reasoning, as follows:
- There is no such thing as the supernatural
- The Gospels report supernatural events
- This must be because the Gospels are unreliable embellishments to the real story of Jesus
- People couldn't have widely published such fictitious accounts in a time/place where people knew what had actually happened
- So the Gospels must have been written after eyewitnesses of Jesus' ministry were dead
The entire exercise presupposes its own conclusion. Because this manner of thinking was pushed to the mainstream of New Testament scholarship by the Tubingen School in the 19th century, New Testament scholarship has seen something of a divide between:
- Scholars who assume naturalism before evaluating the New Testament text (or rely on the work of others who do)
- Scholars who do not make this assumption
Scholars in the former camp regularly assign later dates to New Testament documents than do scholars in the latter camp. Scholars in the former camp must do so, not on the basis of historical evidence, but because late dates for these documents are required by the premises they started with.
A presentation of these arguments can also be found on my channel here.
