The history of medicine reflects a persistent tension between reductionist precision and holistic understanding. While the biomedical model has yielded profound insights into the mechanisms of disease, its explanatory scope has often remained confined to purely physiological processes. It was within this intellectual context that George L. Engel advanced the biopsychosocial model, proposing a paradigmatic shift that challenged the dominance of biological determinism in clinical thought. His framework called for a more comprehensive account of health and illness, one that recognizes the inseparability of biological conditions from psychological experience and social environment.This book undertakes a critical examination of Engel's biopsychosocial model, tracing its conceptual origins, theoretical structure, and enduring influence across disciplines. Far from representing a simple expansion of variables, the model introduced a systemic perspective grounded in general systems theory, emphasizing interdependence, hierarchy, and complexity. In doing so, it provided a language through which clinicians and researchers could more adequately address the multifactorial nature of disease and patient care.The relevance of Engel's work has only deepened in contemporary medicine, where chronic illness, mental health conditions, and health disparities increasingly demand integrative approaches. Yet, despite its widespread recognition, the biopsychosocial model continues to face challenges in operationalization and empirical validation. This volume engages with these tensions, offering both critical reflection and constructive analysis.By bringing together historical insight, theoretical inquiry, and practical application, this work seeks to reaffirm the importance of Engel's vision, inviting you to reconsider the foundations of medical knowledge and to participate in an ongoing dialogue about the future of truly comprehensive care.