The only "science" that I have any familiarity with is psychoanalysis, and I'd like to present my feelings on the concept of a "delusion". I feel that delusions actually occur from the "rational". Delusions are the outcome of an attempt to imprint a rational sense onto irrational data. So, for example, with schizophrenia, you might have a mind prone to lateral processes, "knight's move thinking" and whatnot, and in trying to get a grip on the seemingly nonsensical perception you're dealing with, you attempt to objectify it, "whittle it down" into an organized understanding, which can lead to very weird conclusions of which we've all heard and I don't need to recount. The same goes for dogmatic religion. It is the not the faith in the unseen that I find to be delusional, it's that it becomes concrete truth through law and literal interpretation -- tools of rationality and the most dangerous traits of believers. It's their logic that the delusions kill for.
I want to emphasize this because I feel this understanding supports the idea of interacting with the supernatural through psychedelics as being a helpful mindset. The idea that there are dimensions of experience, perception, mind and consciousness that cannot be understood through logical means MUST be confronted, because these are the dimensions that psychedelics give you the ticket to visit. And I think that the posters here who capitalize the "m" in Mushroom and see it as a spirit teacher, "unified intellegence", conduit to Gaia, etc. are probably the psychonauts that understand this the most. It is these mindsets that accept the psychedelic experience will present something beyond one's own rational perception, and this acceptance I would say protects us from delusion.