This book offers an interdisciplinary perspective on personality disorder with chapters by philosophers, psychiatrists, and psychological scientists. Written to be accessible to all three disciplines, it updates traditional conceptualizations and offers new and novel perspectives on personality disorder, with a special emphasis on borderline and narcissistic personalities. Featuring contributions from established senior researchers as well as early career scholars from across four continents, it offers surveys of contemporary research and clinical expertise that together plumb the foundational understandings of personality disorder.