Several years ago, Gary Habermas wrote an article discussing some historical problems with the hallucination theory. Modern skeptics who are aware of such problems sometimes try to argue for the same sort of theory under different terminology and with some minor adjustments. Sometimes they'll use the term "vision" rather than "hallucination" and will claim that their proposal of visions can't be dismissed on the basis of problems with a hallucination theory, since they distinguish between visions and hallucinations. But is the distinction sufficient to overcome the relevant problems?
I've come across skeptics who will argue against the resurrection largely by citing alleged historical parallels to the resurrection claims of the early Christians. They'll suggest that those alleged parallel accounts should be rejected, and that we therefore should reject the Christian claims. But three questions need to be asked, questions that skeptics often ignore when they draw these parallels:
1. What reason do we have to think that the alleged parallel incidents are historical in the sense that historical individuals experienced historical visions of some sort? If Christians have to make a case for the historicity of the resurrection appearances experienced by Peter, Paul, and the other early Christian sources, then skeptics have to make a case for the historicity of the supposed parallels they're citing.
2. What reason do we have to conclude that the incident in question was naturalistic? Skeptics can't just assume that an incident was naturalistic in order to have a naturalistic parallel to offer.
3. Are the reasons we have for viewing the incident as naturalistic applicable to the incidents in early Christianity? For example, nobody denies that people can have naturalistic visions, hallucinations, or whatever we want to call them under the influence of drugs. But if it's unlikely that people such as Peter and Paul had drug-induced experiences, then citing a drug-induced vision as a parallel to the resurrection experiences of the early Christians wouldn't make sense.
Skeptics can't just cite a reported occurrence of a visionary experience, assume without evidence that some sort of visionary experience did occur, assume without evidence that the experience was naturalistic, and assume without evidence that the circumstances surrounding that experience are comparable to those surrounding the resurrection appearances in early Christianity.