While perhaps at first sounding plausible, many factors contradict such a notion.[2] To name a few:
The large number of witnesses (hundreds) (1 Corinthians 15:5-8)...
Covering the spectrum of personality types (e.g., John 20 -- Peter, Thomas, the two Marys, etc.), contradict the theory of hallucinations which, by definition, are not shared experiences.
There is no such thing as a vision appearing to a crowd. It's generally received only by one person at a time, and that person must be expecting the vision and be in a highly emotional state. As the Bible shows, none of Jesus' followers expected him to rise from the dead. Luke said that when Jesus appeared to the disciples, "They were terrified and frightened, and supposed they had seen a spirit" (Luke 24:37).
Mistaken identity can not be the explanation, either. Certainly the disciples would recognize the person they had been with every day for more than three years.