Silverstone writes: "One of the widely misunderstood issues is that mental-health professionals will only make a diagnosis such as psychosis when someone’s beliefs are not compatible with those held by others – no matter how odd or unusual they may be."

What exactly does he mean? Is it that it mistakenly believed by the general public that (i) mental-health professionals will diagnose S as psychotic (say) only if S's beliefs are not compatible with those held by others? Or is it that (ii) if S's beliefs are not compatible with those held by others, then mental health professionals will diagnose S as psychotic? It is by no means clear.

He goes on to say: "This means that people who belong to small groups with unusual beliefs do not receive mental-health diagnoses." What does 'this' refer to? The mistaken belief. If so, it is hard to see how it follows from either (i) or (ii). 

The article raises important issues but it is neither well-written nor well-edited.