In light of recent posts I will hold off on the lengthier posts unless the unthinkable happens and someone asks me to finish them. Here I will just share why I personally find the hallucination theory to be extremely unbelievable:
If a man was arrested for stealing motor oil from an auto parts store, and he claimed that he was doing it because an alien appeared to him and asked him to do it, and if he stuck to that story even in the face of prosecution, we would all be justified in dismissing him as a liar or a lunatic. If, on the same night, a group of other people were arrested for stealing motor oil from a different auto parts store, and if they all claimed that an alien fitting the other man's description appeared to them at various times and asked them to steal motor oil, and if they all stuck to this story in the face of prosecution, we would begin to think something was amiss. Perhaps a conspiracy, or a prank - but why would they all be willing to face the charges if it was made up? If, along with all this, a man who had formerly been an outspoken skeptic of alien visitations suddenly claimed to have had a similar visitation, and (barring any charges for stealing motor oil) he committed himself to leading a group of people dedicated to telling the world about this alien, we would all be very confused (especially if his initial 'skeptic' status was verified). Finally, if one of the arresting police officers suddenly claimed to have witnessed the alien himself, who made the same request for motor oil, and the officer joined in with the stealing and was thus arrested, but stuck to his story in the face of prosecution, citing the event as mere hysteria or hallucination would be dishonest.
It does not mean we would be under an obligation to believe in aliens. It only means that, on the basis of all this testimony, we would have to believe that something outside of the minds of all these individuals was causing these experiences. In other words, we would acknowledge these as having been real experiences of something as of yet undetermined. Of course if it is outside their minds, then it cannot have been hallucination. I believe we have a similar situation with the claims of the disciples, Paul, and James.