Muslims and even some atheists claim that St. Paul’s writings are forgeries, but what is the evidence that the writings of St. Paul are authentic?
All of Paul's writings, save Titus & Philemon, are quoted within a generation of Paul's lifetime, by people who were in a position to know who wrote them. Many of Paul's letters are quoted by Clement of Rome, who knew Paul personally.
All of Paul's writings, save Philemon, are quoted within 2 generations of Paul's lifetime, by well-informed scholarly writers.
(for Philemon--which is short enough there's not much material to quote =)--we have to wait for Tertullian for our first surviving scholarly citation).
Additionally, every surviving manuscript of the 13 Pauline letters (Hebrews excluded) is attributed to Paul.
Our evidence that Paul wrote these letters is not 2000 years removed from the composition of these documents; in almost all cases it is within a few decades of when the documents were written, and some of this evidence comes from people who knew Paul personally.
For a chart of citations of Paul's work by early scholars, see here.
The Pastorals (1 Timothy, 2 Timothy, Titus) are the works attributed to Paul that are most often accused of being forgeries. For a brief, critical review of these accusations, and the assumptions upon which they rest, see my work here and here.
What is the evidence for the legitimacy of St. Paul’s writings?
Hold To The Rod has demonstrated quite well the legitimacy of St. Paul’s writings. I simply wish to add a few points here.
To me the best criteria to show their authenticity would be the the Early Church in no form or fashion would have accepted the Epistles of St. Paul if they were deemed forgeries.
Some have made the claim that there are forgeries amongst them because the style, wording, language, etc. Are different between some letters.
For that matter, I have done that in many of the posts I have written here on Christianity SE. Some posts are more personal, while others are a more matter of fact like. The differences do not prove that I did not write those different posts. People, including St. Paul, can freely write in a various manners according to their inspiration, insights and the intended target audience. No problem in my books here.
The Critics’ Arguments
The critics’ arguments that someone else wrote Paul’s three Pastoral letters to Timothy and Titus are based on five main issues. Historical references in Paul’s letters are not consistent with the account of Paul’s life in the book of Acts.
The false teaching described in his letters was a clear reflection of the Gnosticism of the second century.
His descriptions of the church’s structure better describe the church of the second century and not of his time, the first century. His letters don’t contain the themes of his theology.
The Greek vocabulary in his letters contains words not found in Paul’s other letters, nor in the rest of the New Testament.
These arguments are unequivocally and absolutely dismissed by theologians as we’ll see.
Argument #1: The incompatibility of the timeline is because the narrative of Acts ends with Paul’s first imprisonment in Rome, not with his death. The argument could only be true if Paul was never released from jail, but we know he eventually was. He even knew he was going to be released (Philippians 1:19, 25–26; 2:24; Philemon 22), and his death did not occur for many years.
Argument #2: Theologians agree there are some similarities between Paul’s dissent in his three letters and second-century Gnosticism. However, unlike Gnosticism, false teachers, who based their teachings on Judaist legalism, were still in the church (Colossians 1:7; Titus 1:10,14; 3:9).
Argument #3: The church’s organizational structure is quite consistent with Paul’s writings such as in Acts 14:23 and Philippians 1:1.
Argument #4: Paul’s Pastoral letters do mention the central themes of his theology: the divine inspiration of Scripture (2 Timothy 3:115–17), election (2 Timothy 1:9; Titus 1:1–2), salvation (Titus 3:5–7), the deity of Christ (Titus 2:13), his personal calling by Jesus (Titus 2:5); and substitutionary punishment by Jesus for our sins (Titus 2:6).
Argument #5: The Greek vocabulary and subject matter were necessary because of the audience it was written for. The Pastoral letters were personal letters to Timothy and Titus, who were both Greek.
Theologians further point out…
The early church never would have tolerated forged letters as part of Scripture.
If they were forged, why weren’t the changes made so everything was consistent with Paul’s other writings?
If the letters were written by dictation, does that still count Paul out as the original author?
Finally, why would Paul warn us about deceivers (2 Timothy 3:13; Titus 1:10) if he was one himself? That doesn’t make sense. He would have blown his own cover, in a sense.
We can only conclude, then, that Paul’s three supposedly forged Pastoral letters were indeed written by him shortly after his release from his first Roman imprisonment. The only exception is 2 Timothy. That letter — his last letter — was written after his fifth and final missionary journey and during his second Roman imprisonment just before his martyred death in 67 A.D.
One interesting side note is that Jerusalem’s second temple (sometimes called Herod’s temple) was burned to the ground just three years after Paul’s death. The third temple won’t be built until the days when Jesus returns during Tribulation. - Who Wrote Paul’s Letters in the New Testament?