It might seem puzzling that I am stressing the role of schizophrenia in the events of the weekend, when in earlier posts, I have spoken in broadly Szaszian terms about the unreality of mental illness. There is no contradiction; I always thought Thomas Szasz was wrong about schizophrenia.
There are three categories: neurological impairment, functional mental illness, and socially disapproved conduct. The existence of neurological impairment is uncontroversial: Rep. Giffords is suffering from it right now. The existence of socially disapproved conduct is equally uncontroversial. What is questionable is whether there is any such thing as mental illness other than an ideological fantasy which we use to interpret socially disapproved conduct, given that the only basis for attributing it is to interpret conduct as medical symptom without any independent criteria for neurological impairment. Merely being able to correlate socially disapproved conduct with neural phenomena is insufficient, since all behavior correlates with some neural phenomena, and with mental illness, socially disapproved conduct is the sole basis for the classification of the neural phenomena as abnormal.
In order to show that something is a neurological disorder, one must have an independent account of what proper functioning for nervous systems is, and a cause of deviation from it which is not itself psychological or social. Unfortunately, the causes of all neurological disorders have not yet been discovered, which means that there will be patterns of conduct whose proper classification is uncertain. In the case of schizophrenia, though we do not yet know its cause, the preponderance of the evidence suggests that it is a neurological disorder, and some evidence suggests that it may be caused in part by the toxoplasmosis parasite.