A lot of critical-leaning biblical scholars dispute Paul’s authorship of the Pastoral Letters: 1 Timothy, 2 Timothy, and Titus. Recently there has been a bit of movement toward greater acceptance of the possibility of Paul’s authorship among those more critically inclined, though there is still a long way to go. One argument supporting the Pauline authorship of these letters is a discovery I made a number of years ago while studying Polycarp’s Letter to the Philippians. Polycarp inadvertently tells us in his little letter that he believes that the Apostle Paul is the author of 1 Timothy and 2 Timothy (and if that is true, probably also of Titus). Why does this matter? Because Polycarp wrote around A.D. 120 (some recent scholars say around 110), and was in a position to know a lot about the apostolic age that we don’t know. Up until this discovery, the earliest known author to both quote from the Pastoral Letters and to connect them to Paul as author was Irenaeus writing around A.D. 180. This discovery moves down the external attestation for the Pauline authorship of the Pastoral Letters by 60 years.
Basically, the argument hinges upon two observations, both pretty obvious once they’ve been pointed out.
Observation #1: The first is that Polycarp clusters allusions to Paul’s writings around each of the three times that he mentions Paul’s name explicitly (in chapters 3, 9, and 11). You see, Polycarp is like some elderly Christians you may have met in your life who are so immersed in the Bible that they almost talk like the Bible. Polycarp had huge sections of the Old and New Testaments committed to memory. His letter could almost be described as a pastiche of allusions to various writings, about half of which are originally Paul’s. (His connection to Paul in this letter makes sense, of course, since he is writing his letter to a Pauline congregation….the Philippians!) Polycarp pretty randomly mixes allusions to Paul’s writings (half of his total allusions) with allusions to other writings (e.g., Psalms, Matthew, 1 Peter, 1 John). But there is one significant exception: when he mentions “Paul,” he clusters allusions to Paul right after the mention of his name. He does this all three times he mentions Paul, showing that this is a pattern.
Observation #2: In the first “cluster” of Pauline allusions are two clear allusions to 1 Timothy (1 Tim. 6:10 and 6:7 found in Pol. Phil. 4.1) and in the second “cluster” is one clear allusion to 2 Timothy (2 Tim. 4:10 found in Pol. Phil. 9.2). There are none from the Pastoral Letters in the third cluster.
The implication of the first observation is that Polycarp considers the phrases in each cluster to be Pauline. The implication of the second observation is that Polycarp considers the phrases which he quotes from 1 and 2 Timothy also to be from Paul.
This, of course, doesn’t prove that Polycarp is correct in his assessment. But, as Koester writes, Polycarp was “doubtlessly the most significant ecclesiastical leader of the first half of II C. E.” If anyone in the post-apostolic church was in a position to know the answer to this question, Polycarp of Smyrna was.
For full argument, see chapter 4 of Kenneth Berding, Polycarp and Paul: An Analysis of Their Literary and Theological Relationship in light of Polycarp’s Use of Biblical and Extra-Biblical Literature (Leiden: Brill, 2002), 142-155 and an article on the same subject: Kenneth Berding, “Polycarp of Smyrna’s View of the Authorship of 1 and 2 Timothy,” Vigiliae Christianae 53 (1999): 349-360. Apologists and authors of introductions to the New Testament would do well to add this argument to other older arguments defending the Pauline authorship of the Pastorals.
 Helmut Koester, History and Literature of Early Christianity, vol. 2: Introduction to the New Testament (Philadelphia: Fortress Press and Berlin: Walter de Gruyter, 1982), 308.