Michael -

You raised the example of epilepsy as a brain disease that was first identified by its affect on behaviour. You pointed out that this disease was incorrectly classified as mental illness and that this classification led to unfortunate consequences for sufferers of the disease. I don't deny that there are brain diseases, nor that these diseases can affect behaviour, nor that the first indications of a brain disease may be behavioural. I do deny, however, that there is such a thing as mental illness. In the epilepsy example you in fact agree that epilepsy is not a mental illness. Your example is a fine example of the dangers of taking a set of behaviours and attributing them to a mental illness.

The term "mental illness" is an oxymoron. That which is mental cannot become ill. You say that the brain is the organ of behaviour. This is like saying the stomach is the organ of digestion or that the heart is the organ of circulation. But to make this analogy is to miss a crucial difference. People act according to the theories and values they hold to be true. Stomachs and hearts do not. To understand a stomach or heart, physics and biology suffices. To understand behaviour, we need non-physical modes of explanations. For example, George Bush's took the decision to invade Iraq because he believes that defeating certain types of tyranny is the best way to prevent future terrorist attacks. Knowing just the neurochemistry of George Bush's brain would not enable us to figure that out. George Bush's theories and values cannot become ill, or be infected with disease, although he may change some of his theories and values as a result of becoming ill. Now holding certain theories and values may cause distinctive changes to the brain, but we cannot "cure" a person of their theories and values by physically trying to undo the changes. That is to misunderstand how knowledge generation works.