From my experience with people who have abused psychedelic narcotics, it is simply creepy the sort of spiritual (not religious) experiences they had - but never positive. People who are virtually illiterate have told me experiences that are simply shocking seeing as they certainly couldn't know about, e.g., demonology. There's also an uncanny resemblance to claimed UFO experiences.

But more to your question, I don't see any issue with resemblances to authentic (as it were positive) spiritual experiences and what really is merely a psychedlically induced one (a pure hallucination). Everytime we sit through a Hollywood movie there are similarities also on the side of the unreal being made to seem to be real. Indeed, we could all very easily be fooled insofar as we grant credence to imagery, which every young person who opened up MS Paint and played around by including pictures (making image composites) knows perfectly well how easy it is to make something totally fake at least look real enough.

Do you mean do psychedelic experiences involve genuinely paranormal states or entities? I'm inclined to say yes. I think that they involve contact with what might be called levels of reality other than the material or corporeal world. 

But the term religious experience suggests a spiritually beneficial experience, and I don't think this is generally the case. I think modern use of psychedelics for spiritual purposes reflects a spiritually laziness and unserious approach to the divine. There are no shortcuts in spiritual matters. At best, such experiences might awaken a desire for something more than the material or help to loosen the chains of today's quasi-materialistic mindset. Traditional shamanic use is  a different matter. This tends to be part of proper religious rites and to take place within a proper imaginal framework, and is something quite different to modern usage of psychedelics.

Jeremy Taylor wrote:

But the term religious experience suggests a spiritually beneficial experience

Oh, I thought it was any extra-normal "spiritual" religiously significant experience, including, for instance, bad experiences, like possession or buddha being visited by the tempter Maru.

iwpoe wrote:

Well, I'm actually inclined to press the opposite way. Is there any reason we shouldn't consider them legitimate?

Maybe my question amounts more to this:

3. By what criteria do we distinguish a hallucinatory religious experience from a genuine one?
3a. I would add that the usual Ideas I hear bandied around, including unorthodoxy of experience or negativity of experience, don't seem to me to be relevant, since it's entirely possible to have a deceptive religious experience in most religious traditions, deceptive with respect to the object, as Satan is with Christ in the desert, or deceptive with respect to the subject, as when somebody experiences something but understands it wrongly.

It also occurs to me that the fact that the circumstance includes usual problems with the perception of everyday reality might not be relevant. Since, for instance, we might not want to exclude experiences had during dream state, Near Death, reverie, some meditative states, fasting, etc.

One way in the case of drugs might be to consider what the natural consequences of taking the drug are in various doses for various people. From that you might get an idea of what is typical or ordinary (really just the effect(s) of the drug) or something extraordinary. That, in turn, may again have perfectly natural causes too but if those causes aren't present then presumably we at least have a candidate for an extraordinary experience.

Is there a proper naturalistic understanding of an hallucination anyway? What is an hallucination, in philosophical terms? As a Platonist, I'd be inclined to think such experiences are connected to the psychic or subtle realms, in one sense or another.

 ​Interestingly, I think Jung concluded that there are clear shared images that occur again and again within hallucinatory phenomena and also psychiatric disorders. By the end of his life he had become convinced that such images are of a more than naturalistic provenance.