Pretty much all of psych constructs are ill-defined, from IQ to autism to schizophrenia. That's not to say intelligence or mental illness isn't real, only that

Pretty much all of psych constructs are ill-defined, from IQ to autism to schizophrenia. That's not to say intelligence or mental illness isn't real, only that psychologists have done a spectacularly bad job at accounting for it in a scientifically valid way.