James the son of Zebedee (John’s brother) died in 44 A.D. and that would be too early for him to write the book of James (Acts 12:2). James the son of Alphaeus or James the Less, another apostle of Jesus (Mark 3:18), was not credited in writing any surviving materials, which makes him an unlikely candidate. The last option seems to be the best. James the brother of the Lord Jesus and the brother of Jude (Mark 6:3) who was an unbeliever in Jesus’ ministry prior to the cross (John 7:5), but believed after the Resurrection (1 Cor. 15:7). He is the prominent leader in Acts 15 of the Jerusalem Church, which is interesting in connection to the Epistle being addressed to the “twelve tribes in the Dispersion” (Jas. 1:1).
2 Peter is interesting as it has a lot of similar material to Jude, which the church also doubted because of the citation of the apocryphal book of 1 Enoch in Jude 1:14. 2 Peter was further doubted because of the many pseudo-writings in the name of Peter as The Acts of Peter and the Revelation of Peter that were circulating at that time. Some have said that the Greek of 2 Peter is different than that of 1 Peter, but Christian scholars have replied by noting that 1 Peter was written by amanuensis by its own admission (1 Pet. 5:12). Therefore, Peter could have used another amanuensis or written 2 Peter himself. There is also the different usage of Greek vocabulary because of the main subject of the two Epistles. 1 Peter was written to help suffering Christians, while 2 Peter was written to battle false teachers within the church.
Jude identifies himself as “a servant of Jesus Christ and brother of James.” This is the James of the epistle of James, the brother of the Lord. Neither James nor Jude (or Judas) call themselves brothers of the Lord because of their humility and felt-unworthiness, they call themselves a doulos, a slave of Christ (Jude 1:1; James 1:1). James and Judas (Jude) are said to be among the brothers of the Lord in Mark 6:3, who were not believing, but became believers after the Resurrection. Since the writing is from a close associate of the apostles, from the brother of the Lord, it is, therefore, to be accepted.
2 and 3 John were doubted because of the size of the volumes. 2 John having only 13 verses and 3 John 14 verses. They seemed so insignificant because of the other volumes that were written by John like the gospel with 21 chapters, the Revelation with 22 chapters and the first epistle of John with 5 chapters (not suggesting that John divided his writings by chapters or that the early church did that). The church seemed to think that 2 and 3 John were not important, and probably were pseudo-writings. The other thing is that John identifies himself as the “elder” (2 John 1:1; 3 John 1:1), unlike in 1 John which has no introduction of the author much like the Gospel (1 John 1:1; John 1:1). Peter used the term “elder” to refer to himself in 1 Peter 5:1, which is not the equivalent of “not an apostle.” Apostles could be elders, as Peter was. Therefore, John referring to himself as an elder does not cast a shadow on identifying him as John the apostle.
Hebrews was doubted because of the author thereof did not identify himself. It’s not that anything was wrong with the theology of Hebrews, but it had to do with the criteria of apostolicity. It came to be accepted as a letter by Paul, although ...