One naturally asks whether we can be sure that the letters attributed to Paul are in fact his. A partial answer is that a forger would run into difficulty. If he wrote a letter, say, to the church at Corinth during Paul's lifetime, and signed Paul's name, the Corinthians would naturally mention it the next time they sent a message to Paul, and Paul would naturally reply: "What are you talking about? I never wrote anything like that!" If a letter supposedly to Corinth were circulated after Paul's death, sooner or later a copy would reach Corinth, and the members of the church there would ask, "If Paul wrote this letter and sent it to us while he lived, how does it happen that no one here has ever heard of it?" Thus, it would be difficult to obtain credence for a forged letter to a congregation. This argument does not apply to a letter to an individual (such as Timothy or Titus). Moreover, it arguably does not apply to the Letter to the Ephesians. Although some ancient copies of this letter begin:
Paul, an apostle of Christ Jesus by the will of God, to the saints who are [at Ephesus and] faithful in Christ Jesus:
other ancient copies read simply "also" instead of the bracketed words. Thus, it is widely supposed that the letter was written as a general form letter to many churches, with the name of the church to be filled in in each particular copy. This view is supported by the fact that the letter contains no personal greetings and makes no references to the past history of the congregation addressed. Now, a forger might write such a form letter, circulate it after Paul's death, and escape detection, since no particular congregation could say, "Since we did not hear of this letter before, Paul could not have written it." And accordingly, we find that it is precisely Ephesians and the Pastorals (the letters to Timothy and Titus) that are questioned by some scholars who acknowledge Paul's authorship of all the other letters claiming to be by him. (I am not counting the letter to the Hebrews, which is not signed.)
Our other source of information is the Book of Acts, where Paul (at first called Saul) appears in 7:58-8:1; 9:1-30; 11:25-30; 12:25-28:31. Here we read how Paul at first opposed and persecuted the Church, how he had a vision of Christ and was converted, and devoted the rest of his life to spreading the Gospel of Christ.
Portions of this account include statements like "we then crossed over to Troas," which are taken to mean that Luke was a companion of Paul for part of Paul's journeys. Since these accounts, particularly those of the shipwreck on Paul's last voyage, show every sign of being accurate eyewitness accounts (see the book The Voyage and Shipwreck of Saint Paul, by James Smith of Jordan Hill, FRS) and since a comparison of the style of various portions of the Book of Acts makes it highly improbable that it is a scissors-and-paste job, with portions of one man's work inserted into a story by someone else, many scholars consider the claim that Acts was written by a companion of Paul to be well established.
On the other hand, it is not always clear how the chronology of Luke's account of the life of Paul is to be fitted with the autobiographical snippets we find in Paul's own writings, and for this reason some scholars dispute the genuineness of the Book of Acts.
For an old but still worth-while introduction to the subject, and a defense of the conservative position, I refer the reader to A Historical Introduction to the New Testament (the title varies a bit from one edition to another) by George Salmon, FRS.
written by James Kiefer
[note: an FRS is a Fellow of the Royal Society]
O God, who by the preaching of your apostle Paul have caused the light of the Gospel to shine throughout the world: Grant, we pray, that we, having his wonderful conversion in remembrance, may show ourselves thankful to you by following his holy teaching; through Jesus Christ our Lord, who lives and reigns with you, in the unity of the Holy Spirit, one God, now and for ever. Amen.