Genomicus writes:
It's fairly difficult to prove a negative.
That depends on the negative. I'm sure I could prove that I'm not a women, not Chinese, and not a frog. "Mental illness" isn't clearly defined, and could be regarded as a matter of degree. But if a specific condition with specific symptoms was defined, then reasonably demonstrating the negative in individuals should be possible, even in some cases on a discussion board.
For example, there's a certain type of language problem associated with some forms of schizophrenia, and there have been several posters on EvC during my time here who might have had this problem. It's always hard to be sure, and I wouldn't be able to prove the positive on internet discussion board evidence alone. But I can be sure that you and all the other regulars who are on this thread so far do not have it.
That's just one symptom of one kind of mental illness, of course.
Geno writes:
E.g., it's very, very hard to prove something could not have evolved.
There's no reason to suppose that that would be the case if we actually
were in a created biosphere.
Off topic, unfortunately, but just sayin'.