Some scholars have argued that the practice of writing a letter in someone else's name ("pseudonymity") was culturally accepted in NT times, and hence they claim that some of the NT letters were not written by the purported authors. For example, it is often claimed that Paul did not write 1-2 Timothy and Titus, or that Peter did not write 2 Peter. But the evidence is lacking that pseudonymity was accepted in letters that were considered to be authoritative and inspired. For instance, in 2 Thessalonians 2:2 Paul specifically criticizes those who claim to write in his name, and he concludes the letter with assurance that the writing is authentically his (3:17). The author of the NT apocryphal book Acts of Paul and Thecla was removed from his post as bishop for writing the book as if it were by Paul, even though he claimed that he had written out of love for Paul (Tertullian, On Baptism 17). In the same way, the Gospel of Peter was rejected as an authoritative book in a.d. 180 by Serapion, the bishop of Antioch, because it was not authentic, even though the author claimed that it had been written by Peter. Serapion said, "For our part, brethren, we both receive Peter and the other apostles as Christ, but the writings which falsely bear their names we reject, as men of experience, knowing that such were not handed down to us" (Eusebius, Ecclesiastical History 6.12.1-6).
There is no convincing evidence, then, that pseudonymous writings were accepted as authoritative. Indeed, if Peter did not write 2 Peter, then the author is guilty of deceit and dishonesty because he claims to have been an eyewitness of the transfiguration (2 Peter 1:16-18) and identifies himself as Peter at the beginning of the letter (2 Peter 1:1). In the same way, the Pastoral Epistles (1-2 Timothy and Titus) all claim to be by Paul and communicate many details from his life, which would be quite deceptive if Paul did not, in fact, write the letters. Some of the authors may have employed a secretary (amanuensis) to assist them in writing, which might account for some of the stylistic differences in the letters. Still, each letter would have been carefully dictated and reviewed by the apostolic author.