In 1979 Bruno de Finetti gave a course at the "National Institute for Advanced Mathematics" in Rome. Alberto Mura took part in that course and agreed with de Finetti to record it on tape. What appears in this volume is Mura's transcription of the 19 course sessions, taking the form of a seminar. The result is a very interesting book, containing many insightful remarks, which throw new light on the thought of the most outstanding representative of the subjectivist approach to probability.