This semester, in my Landmarks in Philosophy class, I used Thomas Szasz‘s The Myth of Mental Illness as one of the three texts on the reading list (The other two were Mary Wollstonecraft’s Vindication of the Rights of Woman and William James’ Pragmatism.) Szasz’s argument that mental illness does not exist, that psychiatry is a pseudo-science was, as might be expected, fairly controversial; critics accused him of overstating his case and of drawing too sharp a boundary between the physical and the mental. Be that as it may, there are many, many acute insights in Szasz’s work; these continue to make reading his work a useful experience for any philosophy student.
Among these insights, in no particular order, are the following:
1. Reducing the mental to the physical comes at a cost of explanatory power. Especially when such reduction is merely offered in the form of a promissory note; many existing behavioral disorders still lack physical correlates in neurophysiology. The languages of the mental and the ethical often offer us richer and more useful explanations for understanding our fellow human beings than the language of the physical; many phenomena of social and ethical interest ‘vanish’ when subjected to the lens of the physical.
2. The so-called ‘mentally ill’ are engaged in a species of communication with us; it behooves us to try to translate their ‘speech.’ This leads to a consideration of a hierarchy of languages and a study of the metalanguage and object language distinction.
3. The category ‘mentally ill’ functions, all too often, as a catch-all category used to lump in socially undesirable behavior; what counts as desirable and undesirable is clearly a function of existing social prejudices. The infamous DSM criteria often encapsulate such prejudices; unsurprisingly these need to be revised over time to accommodate such inclinations. (Remember that Dostoyevsky’s ‘Underground Man‘ was a ‘sick man.’)
4. A game-playing and rule-following model of human behavior offers us interesting and useful interpretations of social situations and interactions within them. (Wittgenstein’s notion of language as a kind of social game immediately comes to mind here and allows for a fruitful investigation of this claim.)
5. Medicine functions within a social, economic, political, and ethical context; the rights of patients and healers emerge within this context. We should expect medicine to be practiced differently–with different medical outcomes–in different contexts. From this, a larger point about the social construction of science, scientific practice, and scientific knowledge can be seen to follow; the boundaries of science are very often informed by social and legal considerations. Consider, for instance, the testing of cosmetic products or new drugs on laboratory animals, experimental procedures which stand and fall depending on whether they have received legal sanction from the surrounding legal regime.
6. The autonomy and personality of the patient is a moral good worthy of respect; the practice of medicine and the relationship between the doctor and patient should be cognizant of this. (The notion of ‘informed consent’ in modern bioethics can be seen to be powerfully informed by such a consideration.)
Samir Chopra 
As a behavior analyst, I would suggest a third option for number 1. That is, rather than reducing the mental to the physical, we can reduce it to the measureable and observable. In my practice, I rely on deterministic principles in my work with behavior change. By altering antecedent and consequent events, which are very physical, we can have effects on behavior, which are also physical.
Now, the actual physiological processes involved are still quite mysterious. However, the science of behavior is vastly less so!
Eli, thanks very much for that thoughtful comment. I agree entirely; behavior is tangible and visible and amenable to intervention.