The subject of the book is the culture of crisis and controversy that exists in contemporary mental health research, following the publication of the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and the National Institute of Mental Health’s declaration of it as unfit for guiding research in psychiatry. The book explores both the nature and sources of the crisis as well as whether and, if so, how, it can be overcome. It brings together a collection of original articles that develop and apply various analytical ideas and strategies from the philosophy of science, and from other relevant areas of philosophy and science, with the aim of clarifying some aspects of the current crisis and the associated extraordinary science. The themes of the chapters include understanding the research domain of mental illness, clarifying the nature of the problems that constitute the current crisis, identifying key substantive and methodological assumptions concerning classification and research focused on the domain of mental illness, identifying ideas bearing on how best to respond to the current crisis with respect to the scientific research agenda, and constructively addressing the tension between pursuing a progressive scientific research program concerning mental illness and maintaining a place of prominence for individual persons and their contexts.