Paul Diel (1893–1972) was a French psychologist of Austrian origins. Building on the work of Freud, Adler, and Jung, he developed an original technique of introspection and analysis designed to expose the secret inner motivations that influence behavior. His contemporaries, notably Albert Einstein, recognized him for his penetrating moral vision as well as his scientific rigor. In France, a group of physicians, psychologists, and educators—called the Association de la Psychologie de la Motivation—is devoted to the study and transmission of Diel's work. Other books by Paul Diel in English translation are The Psychology of Motivation, Symbolism in Greek Mythology, and The God-Symbol.