The document discusses attachment theory from multiple perspectives. It summarizes the pioneering work of Bowlby, Ainsworth, and others in establishing attachment theory. It describes core functions of attachment including a safe haven and secure base. It outlines Ainsworth's Strange Situation experiment and the resulting patterns of infant attachment. It discusses attachment relationships beyond infancy and patterns of adult attachment. Finally, it discusses psychotherapy and treatment from an attachment perspective, focusing on the role of a secure base and mentalizing.