Fourteen of the letters in the New Testament are traditionally attributed to Paul: Romans, 1-2 Corinthians, Galatians, Ephesians, Colossians, Philippians, 1-2 Thessalonians, 1-2 Timothy, Titus, Philemon, and Hebrews.
The authorship of Hebrews has always been disputed, based on the language (the Greek used is very different from that in the other 13 letters) and the theological content (most traditional "Pauline" themes--sin, resurrection, Jesus as Lord--are not addressed). Its inclusion in the New Testament canon was disputed.
The remaining 13 letters remained solidly attributed to Paul, despite dissimilarities and even contradictions, until the foundations of modern biblical criticism. Analysis of language, themes, and content led scholars to divide up the 13 letters into three distinct categories, based on the probability of their having been written by Paul.
The idea that some letters were written in Paul's name, but not actually by Paul, is not so shocking a proposition. Certainly an ancient writer--probably a disciple of Paul's, or perhaps a disciple of a disciple--would not have considered himself (or herself) to be doing anything immoral. "Forgery" and "plagiarism" are modern concepts. To write in someone's name was acceptable in antiquity, as long as the writer thought he (or she) was accurately conveying the thoughts and wishes of the author under whose name he (or she) was writing.
Nevertheless, it seems clear to many scholars that Paul's ideas and the ideas of his later followers diverged somewhat, particularly on issues of social convention and morality. (The comparison between 1 Corinthians 7 and the Pastoral Epistles shows this most clearly.)
The chart below shows the terms used to describe the 13 Pauline Epistles based on their probable authorship.
Authentic or Undisputed Letters
Deutero-Pauline or Disputed Letters
Explanation of terms:
Authentic or Undisputed: These are the letters scholars universally attribute to Paul, based on their unity of theme and language and style. They were probably written over the course of a dozen years (from the early 50s-mid 60s C.E.) to communities that Paul had founded, or visited, or was about to visit.
Need a mnemonic device? Red Chilis Give Popcorn That Punch (Romans, 1-2 Corinthians, Galatians, Philippians, 1 Thessalonians, Philemon)
Deutero-Pauline or Disputed: "Deutero-Pauline" means secondary Pauline letters (compare Deuteronomy, the "second law"; or Deutero-canon, the "second canon"), also called disputed letters. Some scholars think these were written by Paul, others do not. There is a certain similarity of language (especially between 2 Thessalonians and 1 Thessalonians); but this might be attributed to a follower of Paul deliberately mimicking his master's style. Other differences, in language and content, lead some scholars to believe these were written after Paul's death (perhaps by 90 or 100 C.E.) by particular factions of his community seeking answers to questions they couldn't find in the 7 authentic letters.
Need a mnemonic device? 2 Tylenol Cure Everything (2 Thessalonians, Colossians, Ephesians)
Pastoral Epistles: These three letters sound the least like Paul (as we know him from the Authentic Letters); in fact, the language and content sometimes directly contradict what is found in the Authentic Letters. Few biblical critics believe these were written by Paul. They were probably written by a particular community that Paul had founded that held certain interpretations of Paul's teachings, perhaps even interpretations that disagreed with other Pauline Christians. They are very socially conservative, and may have been written a generation or two after Paul's death (perhaps as late as 125 C.E.)
Need a mnemonic device? Well, I don't have one--they all start with "T"--that should help, right? 12TT, maybe? If you can think of a good way to remember these three, let me know.
One suggestion comes in: "1 Tomato + 2 Tomato = 3 Tomato"; it's catchy...