The recent discussion of the concept of mental disorder has focused on what makes a mental disorder a disorder. A question that has received less attention is what makes a mental disorder mental rather than somatic. We examine three views on this issue—namely, the internal cause view, the symptom view, and the pluralist view—and assess to what extent these accounts are plausible. In connection with this, three strategies that have been used to pinpoint the mental in psychiatry are identified, namely negative characterizations (the mental as the nonsomatic), exemplification of paradigmatic mental features, and an appeal to intentional content. We also examine different versions of nihilism, the view that the distinction between mental and somatic disorder is ill founded. Finally, it is observed that the discussion of what makes a mental disorder mental has largely been unaffected by conceptions of the mental in the philosophy of mind.