Pierre Janet (1859–1947) is regarded as one of the most seminal researchers, clinicians, and thinkers of the last two centuries. His work spanned the fields of psychotherapy, psychology, and philosophy. Giuseppe Craparo, PhD, is a psychologist, psychoanalyst, and Associate Professor of clinical psychology at the Kore University of Enna, Italy. Onno van der Hart, PhD, is a psychologist, former psychotherapist, and Emeritus Professor at Utrecht University, the Netherlands.