When is a belief system a Mental Disorder?

i think it would instead qualify as wittgensteinian 'mistakenness'.

Imagine that you're a psychiatrist. A new patient comes to see you and says that he regularly talks to an invisible being who never responds, that he reads excerpts from one ancient book and that he believes wholeheartedly that its contents must be accepted implicitly, if not taken literally.The patient goes on to say that that the world is only 6,000 years old and that dinosaurs never existed. He brazenly rejects modern science's observations and conclusions, and subscribes to the notion that after death he will live in eternal bliss in some alternate dimension. And throughout your meeting, he keeps handing you his book and urging you to join him, lest you end up after death in a far less desirable alternate dimension than him.Is this a mentally healthy person? If you were a responsible psychiatrist, how could you answer yes? These symptoms border on delusional schizophrenia, which the American Psychological Association's DSM-IV describes as involving a profound disruption in cognition and emotion, assigning unusual significance or meaning to normal events and holding fixed false personal beliefs.So, should you insist on follow-up appointments along with some strong medication? Well, quite obviously, the patient is a religious fundamentalist. So he would most likely not be diagnosed with a psychological problem. In fact, such a diagnosis could land you in hot water; the patient's religious beliefs are constitutionally protected.Yet, perhaps it's time this changed, and that we made religious fundamentalism a mental and cultural health issue. People should be able to believe what they like, but only so long as their convictions don't harm others or, arguably, themselves. Fundamentalism, however, breeds fanaticism and often leads to terrible violence, injustice and inequality. If society can force drug addicts into rehabilitation because they're a danger to themselves and the public, then we should be able to compel religious fundamentalists to undergo treatment as well.

The patient goes on to say that that the world is only 6,000 years old and that dinosaurs never existed. He brazenly rejects modern science's observations and conclusions, and subscribes to the notion that after death he will live in eternal bliss in some alternate dimension. And throughout your meeting, he keeps handing you his book and urging you to join him, lest you end up after death in a far less desirable alternate dimension than him.

mini ditka writes:I was just reading an article about a man who believed God told him to kill someone and even though he didn't want to do it he felt he had to obey the word of god (his lawyers are claming the insanity defense).
This got me thinking.... Many people hold views that clash with objective reality. When does holding irrational beliefs become a mental disorder? When do these belief systems become a concern for society? I'm interested in all views on the subject and any research that has been done.
Some examples of views that seem to clash with reality and may or may not be evidence of mental problems:
Belief in Magic, Spells, Wizards, Witches, etc Believing the world is 6000 years old Believing that you get 72 virgins through suicide bombing
Believing that Aliens built the Pyramids Belief in crazy conspiracies (think Timothy McVeigh)
Other cult beliefts (ex. UFO cult that committed suicide)
I'm interested in where the line is drawn between just being a "bit of a loon" and having a mental disorder.