Some have proposed Galatians 1:19 as the "smoking-gun" evidence for a historical Jesus. The passage reads:
Many people interpret this passage as referring to James, the biological brother of Jesus. Since Paul is mentioning this James in passing with no apparent motive in doing so aside from informing people, then there's no reason to believe Paul was making up this James, and this "brother of the Lord" probably was a real person. If a blood-brother of Jesus existed, then Jesus existed. I think that this James was a real person, but it's hardly obvious that he was really the biological brother of Jesus. It is true that when we speak of a man's brother, then we normally are speaking of his biological brother. However, in Galatians 1:19 Paul is referring to a man being the brother of the Lord. Generally, people don't think that a man can be a divine being's biological brother. I must then conclude that Paul is not likely telling us that James was the blood brother of Jesus; he more probably understood James as being the Lord's brother in a metaphorical sense. Galatians 1:19 is then not the smoking gun for the historicity of Jesus.But other of the apostles saw I none, save James the Lord's brother.