Betty Cannon, PhD, is a licensed psychologist who has taught and practiced in Boulder, Colorado, for over 40 years. She is the founder of Applied Existential Psychotherapy, a modality she has been developing and teaching to mental health professionals at the Boulder Psychotherapy Institute (which she also founded) since 1989. She is a professor emerita of the Colorado School of Mines, a former senior adjunct professor at Naropa University, and an editorial board member of Existential Analysis and Sartre Studies International. She is the author of Sartre and Psychoanalysis and numerous articles and chapters on existential philosophy and therapy. Her mentor was Sartre scholar and translator Hazel E. Barnes. She is Hazel’s literary executor, and her book on Sartre is dedicated to Hazel. Her current project is a book on AEP entitled In the Spirit of Play: Applied Existential Psychotherapy, whose central theme also inspired today’s lecture. AEP owes a debt not only to the philosophy of Sartre but also to Gestalt therapy, classical and contemporary psychoanalysis, body-oriented psychotherapy, and humanistic psychology––especially the person-centred therapy of Carl Rogers. Betty’s concept of the spirit of play, conceived as an antidote to Sartre’s “spirit of seriousness,” is further inspired by D.W. Winnicott’s idea that psychotherapy is (or ought to be) a matter of “two people playing together.”