In 1 Corinthians 15, Paul’s reply to the Corinthians on the resurrection would have been much stronger if he could have appealed to witnesses to the empty tomb, as he had appealed to witnesses for postmortem appearances. Indeed, modern apologists often ask skeptics to explain the empty tomb, because they think it contributes to the case for the resurrection. Instead, Paul’s quoted formula relies on an appeal to scripture as the basis for knowing that Jesus has been raised, the same appeal to scripture used to justify the idea that Jesus’s death was “for our sins”. That suggests that this formula indicates theological understanding, not personal knowledge of an empty tomb as a basis for believing that Jesus had been raised (This is the argument, as I understand it, that Bart Ehrman makes for why he now doesn’t believe in the empty tomb, from his book How Jesus Became God).
This seems to be evidence that raises the probability that Paul did not cite the empty tomb in his argument because that tradition arose, at the earliest, between the writing of his letters, and the writing of the gospels. We clearly see the theme of Jesus’s post-resurrection physicality expanding as we move from Mark (no original discussion of Jesus’s post-resurrection appearances) to Matthew (the women are told that Jesus isn’t in the tomb anymore, and they touch his feet when he appears) to Luke (first claim that any of the disciples personally looked and saw the tomb was empty, Jesus makes an argument to the disciples that he isn’t a spirit, Jesus eats a piece of fish) to John (More or less the same as Luke, plus an extra appearance to allow Thomas to personally touch his wounds).
This expansion shows that there was a growing need to convince people that the resurrection was more than a ghostly vision, and claims of the empty tomb would fit in with that. That provides a motive for Jesus’s later followers to claim that there had been an empty tomb even if there hadn’t been. The “who would die for a lie” response would not seem to apply since they would not have been killed for their lie about the tomb, but what they thought was the truth of Jesus’s vindication as messiah. The lie about the tomb would have been merely a useful fiction in the service of a worthy cause.
How would you answer this argument?