Some have claimed that Jesus was a celestial being subordinate to God with whom people hallucinated conversations with. The stories of Jesus are full of examples of him touching people, eating with friends, and physical interactions. So with this notion, you have to prove that the gospels are entirely made up. This unprovable premise works best on those that haven’t actually read the gospels (or have read it with powerful pre-conceptions).
They are not written like a work of mythology. If anything they are a record of a string of events where one of the purposes is to prove that Jesus was physically real. It’s my assumption that there are many people that believe the gospels are made up, but have never read them. (hint, hint). Even secular scholars agree that there is at least a kernel of historical truth in the gospels. I of course believe there is much more than just a kernel.
Some have claimed that the disciples experienced a group hallucination. The problem is that we have no recorded case of identical hallucinations occurring simultaneously among multiple individuals. Instead, hallucinations are private, personal, and unique to each who experiences them. To speculate about group hallucinations is not supported by any modern research. Not to mention that a group hallucination would be as much a miracle as the resurrection. Those that claim this happened, are admitting that the miraculous is possible.