Navigating the future of psychiatry requires a firm understanding of its past. This book is intended as a guide for students and practitioners of psychiatry and psychology who seek to understand the evolution of psychiatry as a scientific discipline. Landmark papers covering a broad array of topics are described and their scientific contributions are placed within a historical context. An introductory section sets the stage for the rest of the book, with a presentation of the major foundational constructs of diagnosis and epidemiology. Subsequent sections examine major facets of the theory and practice of psychiatry, namely the pathogenesis of mental disorders, the pharmacotherapy of major mental disorders, psychosocial interventions, and somatic treatments. A final section explores ethical and forensic considerations within the field, as well as suicide and research methodologies. This framework echoes the complexity of psychiatry and psychology, which cannot be reduced to a single set of subspecialty categories.