Who could have written the Pastoral Epistles?

Reading from a preface with a decidedly less orthodox viewpoint on the matter. (i.e. the New American Bible created by those eminent scholars widely considered to be the successors of the Apostles themselves)

From the late second century to the nineteenth, Pauline authorship of the three Pastoral Epistles went unchallenged. Since then, the attribution of these letters to Paul has been questioned.

So tradition goes to Paul, and the age that invented questioning every obvious thing was the first to question their authenticity.

Most scholars are convinced that Paul could not have been responsible for the vocabulary and style, the concept of church organization, or the theological expressions found in these letters.

And whoops, they decided they weren't authentic because they were different.

A second group believes, on the basis of statistical evidence, that the vocabulary and style are Pauline, even if at first sight the contrary seems to be the case. They state that the concept of church organization in the letters is not as advanced as the questioners of Pauline authorship hold since the notion of hierarchical order in a religious community existed in Israel before the time of Christ, as evidenced in the Dead Sea Scrolls. Finally, this group sees affinities between the theological thought of the Pastorals and that of the unquestionably genuine letters of Paul.

But on second thought, they don't seem to be contradicting each other, so maybe someone can write differently when they're writing to different people over the course of ones lifetime?

You can that introduction yourself, but it goes on to suggest two other ideas about the authenticity of the letters, whether the were written by a secretary, which isn't particularly novel considering Jeremiah and Peter. Or that they were compiled from fragments of Paul's writing and added to and redacted over time, which isn't novel either considering Job, Esther and Daniel.

So, 3 out of 4 groups of scholars say Paul and the majority of salvation history is with Paul writing the letters and regardless, most Christians believe it is the inspiration of the Holy Spirit permeating the entire Bible regardless whose hand marked the papyri.

Authenticity

The New Oxford Annotated Bible prologue is correct in stating the Pastoral Epistles (1 Timothy, 2 Timothy and Titus are psuedoepigraphical, not written by Paul.

Bart D. Ehrman, in Forged, page 98, cites the British scholar A. N. Harrison who wrote an important study of the pastoral letters in 1921, giving numerous statistics about word usage. Of the 848 different words used in the pastoral letters, 306 - more than one third - do not occur in any of the other Pauline letters of the New Testament. And two thirds of these 306 words were used by Christian authors living in the second century. Paul not only did not use these words, but it seems he would not have known the meaning of some words that came into use in the second century. Moreover, some ideas and concepts in the pastoral letters stand at odds with what you find in the letters that Paul wrote.

Authorship

Most modern New Testament scholars dismiss the tradition of Paul as the author of the pastoral epistles, to the point that many writers, such as in the New Oxford Annotated Bible no longer feel obliged to give specific reasons for this view. Burton L. Mack says in Who Wrote the New Testament, page 206, the language, style and thought expressed in the pastoral epistles are thoroughly un-Pauline. Although the New American Bible emphasises any doubts about non-Pauline authorship, it still says says in the prologue to 1 Timothy:

Most scholars are convinced that Paul could not have been responsible for the vocabulary and style, the concept of church organization, or the theological expressions found in these letters.

Having ruled out Paul as the likely author of these epistles, we must try to learn what we can of the real author. Because the author wished readers to believe that the three epistles were written by Paul himself, some decades earlier, he was careful to leave us no clue as to his identity.

All we can really infer is that the author wrote during the first half of the second century and probably lived in the Greek-speaking eastern Mediterranean region. The first assumption is based on the references to second-century concepts such as 'overseers', or bishops, and on the analysis by Harrison. Francis A. Sullivan SJ says in From Apostles to Bishops, page 15, that the consensus of scholars, including Catholic ones, is that Rome did not have bishops until around the middle of the second century, so a Roman Christian would have been less likely to have written as if the appointment of bishops was an established fact. The epistle addressees and locations are convenient fictions, so they tell us no more about where our author lived. We can never know the name or any personal details about the author of these epistles.