Paul refers twice to “the brothers of the Lord.” At Galatians 1:18-19 (link), Paul meets James,
Then after three years I went up to Jerusalem to visit Peter, and stayed with him fifteen days. But of the other apostles I saw no one except James, the Lord’s brother.
and at 1 Corinthians 9:5-6 (link) Paul designates a group using the same Greek phrase in the plural,
Have we no right to take along a wife who is a believer, even as the rest of the apostles, and the brothers of the Lord, and Cephas? Or have only Barnabas and I no right to not work?
Religion professor James McGrath, whose ideas on historical reasoning the Uncertaintist discussed last year (link), thinks Galatians 1:19 “ought to settle the matter” that Jesus was a real historical person (link).
It makes sense that if Paul met one of Jesus’ brothers and knew of others, then Paul’s Jesus was an earthly human being. Moreover, these brothers participate in church affairs. Their activity would help explain what Paul thought a living Jesus had contributed to Christian origins, a topic otherwise missing from Paul’s writings.
But no so fast. As with Josephus’ supposed mention of James (link), authenticating excerpts from Paul’s letters isn’t trivial. However, authenticity turns out to be less of a concern for Paul’s the brother of the Lord than for Josephus’ the brother of Jesus called Christ.
Looking past authenticity, to lay the two phrases side by side reveals different levels of discourse. Far from a plain matter-of-fact phrasing, Paul identifies Jesus by a purely religious construction. That being so, how confident can anyone be that Paul isn’t also designating James and the others by another figurative religious construction?