Insanity: Its Causes and Prevention is a comprehensive and insightful treatise authored by Henry Putnam Stearns, M.D., first published in the late 19th century. Drawing upon his extensive experience as a physician and superintendent of a state asylum, Stearns delves deeply into the complex subject of mental illness, offering a detailed exploration of its origins, manifestations, and the societal factors that contribute to its prevalence. The book systematically examines the physiological, psychological, hereditary, and environmental causes of insanity, emphasizing the interplay between physical health, lifestyle, and mental well-being. Stearns discusses the early signs and symptoms of mental derangement, providing readers with practical guidance on recognizing and addressing these warning signals before they progress to more severe forms of illness. He explores the impact of intemperance, overwork, emotional distress, and social pressures, as well as the role of heredity and congenital predispositions. The author also addresses the influence of education, family life, and moral development on mental health, advocating for preventive measures rooted in healthy living, moderation, and supportive social environments. Throughout the book, Stearns combines medical knowledge with compassionate understanding, challenging the stigma surrounding mental illness and urging for humane treatment and care of those afflicted. He offers recommendations for both individuals and society at large, highlighting the importance of early intervention, proper medical care, and the creation of institutions dedicated to prevention and recovery. Insanity: Its Causes and Prevention stands as a significant historical work, reflecting the evolving attitudes toward mental health in the 19th century and providing valuable insights that remain relevant to contemporary discussions on mental illness and its prevention.