Gary: We know that Paul was prone to visions and Paul specifically states in Acts 26 that he only saw a talking bright light…in a vision. A bright light is not a body and a vision is not reality.
Regarding the “500”, we only have ONE source that makes this claim. Yes, most scholars believe it is a very early Creed, but no details of this appearance is given. If Paul believed that Jesus had appeared to him when he had only seen a talking bright light on a desert highway, how do we know that the 500 didn’t have a similar experience?: They all saw a bright light or something that they believed to be Jesus. And one important point: the Creed in I Corinthians says that Jesus “appeared” to the 500, it says nothing about Jesus speaking to them, touching them, or letting them touch him. Therefore the “appearance” of Jesus to the 500 could have been no different that the appearance of the Virgin Mary to THOUSANDS of Roman Catholics.
What about James? Again, we have only ONE source that claims James received an appearance. No where in the Gospels is such a claim made. Could the brother of Jesus have had a vision similar to Paul’s, seeing only a bright light? Sure. Once again, the Creed says nothing about James seeing a “body”, or hearing a voice, or touching a body, or being touched by a body.
Christian: “The belief in the Resurrection itself is very odd, especially in the context of Second Temple Judaism. The beliefs about resurrection have often been oversimplified (see Wright’s The Resurrection of the Son of God for a complete treatment), but it seems very strange anyone would believe in a dying and rising Messiah. Usually, if your Messianic claimant died, you went home or you got a new Messiah (often the brother). I don’t think it’s incompatible with another explanation; it’s possible they were convinced by hallucinations alone. There are some other issues with a hallucinatory hypothesis though.”
Gary: I agree it would be very odd for any Jew to suddenly believe in a resurrected Messiah in first century Palestine as such a concept was unheard of in all of Jewish history. But I see a problem in your theory: If the leader of a new Jewish sect in first century Palestine has been teaching for THREE YEARS that he will die and be resurrected three days later I DON’T think that anyone should be surprised if after the leader’s death, his followers suddenly believe that their leader’s prophesy has been fulfilled when several of them start having false sightings of him and others having visions of him in which he tells them he is resurrected…as he promised.