The two final chapters, by Donald Klein, Robert Krueger, and Daniel Goldman, suggest some avenues to think about with regard to nosology and are particularly relevant in light of work on the upcoming DSM-5 as well as the recently unveiled Research Domain Criteria (1). Klein's chapter starts by discussing the concept of illness as applied to psychiatry and the problem of identifying a proper phenotype that can be later used to discover the factors that could cause that phenotype. Klein advocates the use of therapeutics as a means of identifying potential abnormalities that may be at the core of psychopathological processes, although he recognizes that his approach would require long-term, costly programmatic research. Krueger and Goldman nicely review dimensional approaches to psychopathology, explain how dimensional approaches provide an alternative (and often more powerful) conceptualization of psychopathology, and provide some examples of research questions that can be addressed using a dimensional approach. They end their chapter by advocating a dimensional approach to risk factors, a direction recently followed by Kenneth Kendler in an important study published in the Journal (2).