Let's take a closer look...
The book of Acts is generally considered to have been written by the same author who wrote the gospel of Luke. The reason for this is the reference to "Theophilus" and also the first-person "I" in Acts 1:1 (c.f. Luke 1:3).
However, some scholars doubt that either of these were actually written by the physician that accompanied Paul in the various stories in Acts, despite the accounts being written in the 1st person "we". I won't get into the details of why, but you are welcome to follow this up in this article.
There are some discrepancies between the accounts in Acts and what Paul narrates in his own letters.
For example, did Timothy accompany Paul to Athens or did he stay behind in Berea?
Then the brothers sent Paul away to the coast at once, but Silas and Timothy remained in Berea. Those who accompanied Paul escorted him as far as Athens, and after receiving an order for Silas and Timothy to come to him as soon as possible, they left.
Acts 17:14-15 NET
So when we could bear it no longer, we decided to stay on in Athens alone. We sent Timothy, our brother and fellow worker for God in the gospel of Christ, to strengthen you and encourage you about your faith...Did Paul go to Jerusalem immediately after his conversion, or did he stay in Damascus? Did he consult with just Peter and James, or other apostles as well?
1 Thess 3:1-2 NET
For several days he was with the disciples in Damascus ...
Now after some days had passed, the Jews plotted together to kill him, but Saul learned of their plot against him. They were also watching the city gates day and night so that they could kill him. But his disciples took him at night and let him down through an opening in the wall by lowering him in a basket. When he arrived in Jerusalem, he attempted to associate with the disciples, and they were all afraid of him, because they did not believe that he was a disciple. But Barnabas took Saul, brought him to the apostles, and related to them how he had seen the Lord on the road, that the Lord had spoken to him, and how in Damascus he had spoken out boldly in the name of Jesus.
Acts 9:19-27 NET
But when the one who set me apart from birth and called me by his grace was pleased to reveal his Son in me so that I could preach him among the Gentiles, I did not go to ask advice from any human being, nor did I go up to Jerusalem to see those who were apostles before me, but right away I departed to Arabia, and then returned to Damascus. Then after three years I went up to Jerusalem to visit Cephas and get information from him, and I stayed with him fifteen days. But I saw none of the other apostles except James the Lord’s brother.Perhaps Paul is stretching the truth when he said he saw none of the other apostles. But that makes the very next verse in Galatians 1 a bit awkward when he says:
Galatians 1:15-19 NET
I assure you that, before God, I am not lying about what I am writing to you!On the other hand, I'm not sure why he would say that if his words are supposed to have been divinely inspired. That doesn't make any sense to me.
Galatians 1:20 NET
So, was the writer of Acts divinely inspired to disagree with Paul? or was it the other way around?
Which version of Acts?
Another major point about the book of Acts is that there are actually 2 different versions of Acts in the ancient manuscripts, with one being 10% longer than the other.
There are two major textual variants of Luke-Acts, the Western text-type and the Alexandrian. The oldest complete Alexandrian manuscripts date from the 4th century and the oldest Western ones from the 6th, with fragments and citations going back to the 3rd. Western texts of Acts are 10% longer than Alexandrian texts, the additions tending to enhance the Jewish rejection of the Messiah and the role of the Holy Spirit, in ways that are stylistically different from the rest of Acts. These conflicts suggest that Luke-Acts was still being substantially revised well into the 2nd century. The majority of scholars prefer the Alexandrian (shorter) text-type over the Western as the more authentic, but this same argument would favour the Western over the Alexandrian for the gospel of Luke, as in that case the Western version is the shorter. The debate therefore continues.Note the mention of the book of Acts being "revised" well into the 2nd century. Were the later editors also divinely inspired? Were the earlier editors divinely inspired to get it wrong, such that it required further editing?
Or are we instead looking at documents written by fallible humans?
The letters of Paul
In all of these epistles, Paul does claim to be the author and writer. However, the contested letters may have been forgeries, as that seems to have been a problem among the early church as a whole.
The Pauline epistles are the fourteen books in the New Testament traditionally attributed to Paul the Apostle, although many dispute the anonymous Epistle to the Hebrews as being a Pauline epistle.
There is wide consensus, in modern New Testament scholarship, on a core group of authentic Pauline epistles whose authorship is rarely contested: Romans, 1 and 2 Corinthians, Galatians, Philippians, 1 Thessalonians, and Philemon. Several additional letters bearing Paul's name lack academic consensus: Ephesians, Colossians, 2 Thessalonians, 1 & 2 Timothy, and Titus. Scholarly opinion is sharply divided on whether the former two epistles are the letters of Paul; however, the latter four - 2 Thessalonians, as well as the three known as the "Pastoral Epistles" - have been labeled pseudepigraphical works by most critical scholars.
There are two examples of pseudonymous letters written in Paul’s name apart from the New Testament epistles, the Epistle to the Laodiceans and 3 Corinthians. Since the early centuries of the church, there has been debate concerning the authorship of the anonymous Epistle to the Hebrews, and modern scholars reject Pauline authorship.If you're interested in a fairly thorough look at the reasons why these letters are considered forgeries, I highly recommend reading Bart Ehrman's book, "Forged: Writing in the Name of God".
Were these anonymous authors divinely inspired to write in the name of Paul?
Paul explicitly said some things were his own opinion
To the rest I say—I, not the Lord—if a brother has a wife who is not a believer and she is happy to live with him, he should not divorce her.
1 Cor 7:12 NET
With regard to the question about people who have never married, I have no command from the Lord, but I give my opinion as one shown mercy by the Lord to be trustworthy.
1 Cor 7:25 NET
What I am saying with this boastful confidence I do not say the way the Lord would.Why would God inspire Paul to write these things? It makes no sense at all.
2 Cor 11:17 NET
Now you may be thinking that Paul also claims to have received some things from Jesus, so that if I am to claim that these words indicate human authorship, then the words from Jesus should likewise be treated as divinely inspired. I disagree. My point is not that we should blindly trust what Paul wrote, but rather that these statements are incompatible with divine inspiration. Paul's claim that he received things from Jesus are not incompatible with human authorship. Many people have claimed to hear things from divine beings. I think we could all agree that at least some of them are either lying, hallucinating, or they are simply mistaken. And if it's true for some, then it could potentially be true for all. Therefore, it is compatible with human authorship.
Other Forgeries in the New Testament
There are also other books in the New Testament that some scholars think are forgeries. These are the letters of James, 1 & 2 Peter, 2 & 3 John, and Jude. Although many scholars believe both 1 & 2 Peter are pseudopigraphal (a fancy word for a "forgery"), there appears to be less consensus on the others.
Bart Ehrman, a well-known New Testament scholar, writing in a comment on his own blog, has this to say in response to a question about whether the author of the epistles is the same person who wrote the gospel of John:
The general consensus is that the author of the epistles lived at a later period in the community’s history, but was a different person with a similar theology. The author of Revelation *may* have been connected with the community, but his theology is very different indeed (especially his eschatology). yes, Papias’s “Elder” is often thought to be the author of Revelation. But he’s not (historically) the same as wrote the letters.
A final word on divine inspiration
In this series I've looked at what modern science and scholarship can tell us about the Bible and considered what it all means in relation to the idea of divine inspiration.
I've listed many facts that clearly falsify the notion that God or some other divine being directly dictated the words of the Bible. The idea that the Bible is inerrant is simply indefensible in light of what we now know about the Bible, though many fundamentalists still try. In doing so, I believe they bring the Bible into disrepute, and make it and themselves a target of ridicule.
As a divine product, the Bible is extremely poorly written and contains a large number of contradictions and factual errors. However, as a collection of ancient human writings, it's actually a pretty valuable resource for humanity to study. Simply put, when we drop the silly and obviously absurd notions of inerrancy and divine dictation, the value of the Bible increases substantially.
On the other hand, there also seem to be those who still insist that the Bible was "inspired", but they are extremely vague about both what that means and how it might have come about. To me it seems like an awkward view to even try to defend, especially given that possibly the only mentions that the biblical books might even be inspired come from 2 Timothy and 2 Peter, both now widely considered by scholars to be forgeries!
Yet for some reason these liberal Christians do still insist that the Bible was inspired by God. They just don't say how, and so far as I am aware, they never describe it in any way that would be at all testable or falsifiable. That really frustrates me. Without falsifiability, it's worthless. If you won't tell me how I can test your hypothesis and determine whether or not it is true, then don't waste my time. It's as simple as that.
Is there any reason to believe that the Bible had a divine origin? No.
The simplest and best explanation for the origins of the Bible is that it is an entirely human product of its time.