The 19th century was a defining era for psychology, rich with an intellectual diversity that shaped modern thought but which remains largely overlooked. The roots of 20th century thought can be traced to the 19th century, when a mechanical worldview took hold, society grew increasingly secular, modern urban metropolises emerged, and evolutionist ideas reshaped the understanding of nature’s developmental principles. Throughout this century, the natural sciences extended beyond their traditional limits, influencing and reshaping the human, moral, and social sciences, among which psychology was especially impacted, as this transformation sparked profound debates on the very possibility of a science of the soul. Forgotten Streams in the History of 19th-Century German Psychology recovers the vibrant roots of psychology in empiricism, romanticism, idealism, phenomenology, among other streams of thought that explored consciousness, the soul, and the self before experimental psychology took center stage. Unlike the standard view, this book invites readers to reconsider psychology’s history, revealing a complex landscape that questions the simplistic story of a linear path toward empiricism. Through profiles of significant yet forgotten thinkers, this work uncovers how their ideas contributed to discussions of the unconscious, mind-body duality, and inner experience. Written by leading scholars, each chapter offers a unique window into an intellectual movement that continues to influence debates in psychology, philosophy, and beyond. Essential for historians, psychologists, and anyone curious about psychology’s deeper origins, Forgotten Streams is an indispensable reference that fills an important gap, enriching our understanding of psychology’s complex and multifaceted development.