At last, an original contribution to the once vital field of Family Therapy. Drinking deeply from the wisdom of the exciting founders of the 1970s, the author proposes here an update of remarkable coherence, a veritable new creation of integration. The author has drawn from Bowen¿s classic theory of differentiation, from 21st century brain science of co-creation and from Martin Buber¿s old-new philosophy of I-Thou relating. With alacrity, clarity, humor and human warmth, all of these strands are fully explicated and then skillfully and convincingly woven together. The author draws upon four decades of direct patient care to explain how the different roles a therapist plays must be coordinated with the family¿s level of differentiation. The abundant clinical examples demonstrate this principle in treating couples, families with children and adolescents and coping with various challenges and disabilities. Finally, the levels of differentiation in human service systems are examined and placed within the treatment context.