The purpose of psychiatric diagnoses is to group people who may respond to the same medical treatment together because it has been found that people with similar symptoms respond similarly to treatment. Your use of the term delusional has nothing in common with these aims. Yours is an exercise in pure labeling, an attempt to invoke the stigma of mental illness against those who have religious beliefs. Your labeling is basically a claim that the religious are broken and have defective brains. I don't think this usage is supported by anything we know about the religious. The religious seem just as healthy as non-religious people do concerning non-religious matters. And I would dispute your claim that religious belief is "irrational" (lacking reasons for belief) or unsubstantiated (without justification). Their reasons may not be your reasons, but they are reasons all the same. So what this comes down to is little more than a slur aiming to stigmatize religious belief.
I must also note as a person with schizoaffective disorder who has suffered from delusions the bulk of my adult life, there is a qualitative difference between a bona fide delusion and something that is merely an irrational and false belief. To compare the two as if they were similar only highlights the weakness in relying upon a pat "definition" of what a delusion is, and a distinction between the thinking of an armchair doctor and someone with actual clinical experience.
I would also point out that the belief in invisible sentient beings is not as far fetched as you make it seem. We all seamlessly infer the presence of an invisible mind inhabiting the bodies of other humans we interact with. We even infer a mind behind the eyes of a dog or cat, without the additional component of speech. This "instinct" to infer the presence of non-visible minds is very powerful and operates non-consciously; we do it automatically. It's not that strange that this instinct might misapply itself and infer the presence of invisible minds where they don't exist. This would not be a malfunction of the brain, an unhealthy degenerate condition, but a mere side effect of the brain functioning in its normal manner. If nothing else, this theory of mine points out how intimately intertwined our views of religious behavior are with our theories about why they've adopted this behavior. If you just view religious behavior as a symptom of ordinary belief, you may be missing the true nature of it.
I must also note as a person with schizoaffective disorder who has suffered from delusions the bulk of my adult life, there is a qualitative difference between a bona fide delusion and something that is merely an irrational and false belief. To compare the two as if they were similar only highlights the weakness in relying upon a pat "definition" of what a delusion is, and a distinction between the thinking of an armchair doctor and someone with actual clinical experience.
I would also point out that the belief in invisible sentient beings is not as far fetched as you make it seem. We all seamlessly infer the presence of an invisible mind inhabiting the bodies of other humans we interact with. We even infer a mind behind the eyes of a dog or cat, without the additional component of speech. This "instinct" to infer the presence of non-visible minds is very powerful and operates non-consciously; we do it automatically. It's not that strange that this instinct might misapply itself and infer the presence of invisible minds where they don't exist. This would not be a malfunction of the brain, an unhealthy degenerate condition, but a mere side effect of the brain functioning in its normal manner. If nothing else, this theory of mine points out how intimately intertwined our views of religious behavior are with our theories about why they've adopted this behavior. If you just view religious behavior as a symptom of ordinary belief, you may be missing the true nature of it.