What do you say to the idea that Joseph of Arimathea did not actually exist? Is there good historical proof that he did?
There is no “proof” that any single person lived in ancient history. It is literally impossible to prove that Nero or Julius Caesar or Nebuchadnezzar or anyone else in ancient history lived. What would such proof look like? What we have to ask is what is the evidence that person X lived? What is the evidence, how much evidence to we have, and how reliable is that evidence? I would say that the evidence that Nero, Julius Caesar or Jesus of Nazareth existed is so overwhelming that it would border on irrational to deny that they are real people.
What about Joseph of Arimathea? What is the evidence that he is a real person? The evidence that he is a real person comes from the fact that there are four sources from the ancient world which mention his name and what he did. They are Matthew, Mark, Luke and John. Matthew tells us that Joseph asked Pontius Pilate for Jesus’ body so that he could give him an honorable burial. He wrapped the body in linen and put it in a new tomb, rolling a large rock in front of the tomb. Mark tells us that Joseph was a prominent member of the Jewish council. He gives us some additional information, which is that Joseph had the body taken down from the cross. Luke tells us that the tomb was one which had not yet been used. John tells us that Joseph was a “secret” disciple. He also tells us that Nicodemus accompanied him, adding myrrh and aloes to the body. The point of giving all of this information is that the four accounts are clearly independent accounts. The four accounts are not identical, because each author was either an eye-witness or did his own research.
So, was Joseph a real person? I would say with a 99.9+% certainty that he was a real person. The four gospel writers have every appearance of being reliable in their accounts. Why would all four make up a fake story about a person who never existed? Mark was written in the 50s, or at latest in the 60s AD. Luke and Matthew were both written in the 60s at the latest. This was within thirty or at most forty years from the events. At this time there were many thousands of eye-witnesses to the life and death of Jesus. The church would never have let a gospel writer create completely false events. What would be the motivation? Can anyone even suggest a reasonable explanation for the four separate, independent accounts, other than the only reasonable conclusion, which is that Joseph of Arimathea was a real person. It borders on irrational, given the facts about the four accounts and what we know of the veracity of the gospel writers, and the fact that those who were alive when these things happened were still alive when the gospels were written, to conclude that Joseph of Arimathea was a fictional character.
Some might say that the only accounts of Joseph of Arimathea are Christians, therefore, we cannot trust that he lived. This argument is nonsense, in my opinion. Why would a non-Christian write about this guy? We do not have many historical sources from this time. We have Josephus, a Jewish historian, but why would he mention Joseph of Amirathea? He was not a major character in any of the events that Joseph was concerned with. “Lack of evidence is not evidence of lack” In other words, the fact that person X did not mention person Y is an extremely weak argument that person Y did not exist, unless we can create a strong case that person X ought to have mentioned person Y. In this case, there is no reason that anyone other than a Christian writer would have mentioned Joseph of Arimathea.
In conclusion, we cannot prove that he existed, but there is no rational explanation of the four gospel accounts other than the assumption that he was a real person.