> When, as a result of their obsession with those bizarre fixed beliefs, they are unable to function (hygiene, nutrition, finances, care of their dependents, etc.) - then there’s a problem.
But why does the issue of whether it is “common among their culture” matter? A person unable to function due to a non-bizarre fixed belief has just as big a problem as a person unable to function due to a bizarre fixed belief, if we assume the same degree of functional impairment in each case. The question of whether the belief is “bizarre” seems irrelevant, and possibly even encoding cultural prejudice
But some people’s functioning is impaired by beliefs common to their culture, whereas other people have very unusual beliefs but aren’t impaired by them to anywhere near the same degree
One person obsesses so much over “culture war” topics they lose their job… another person spends all their free time contemplating elaborate idiosyncratic theories of parallel universes, yet still manages to put a lid on it at work to a sufficient degree to keep their job. The first person has a non-bizarre obsession with serious functional impairment (they lose their job due to it), the second a bizarre obsession but the degree of functional impairment is significantly less. So the fact that we label one obsession “bizarre” and the other “non-bizarre” seems of little relevance
If they then become obsessed with the idea being a fact and refuse to even consider updating their mental model when presented with evidence contradicting it then they have developed a fixed belief.
When that fixed belief is not common among their culture, it becomes a bizarre fixed belief.
When, as a result of their obsession with those bizarre fixed beliefs, they are unable to function (hygiene, nutrition, finances, care of their dependents, etc.) - then there’s a problem.
Or do you think a mind is a perfect thing that can never be ill?