This work represents the summary of a course in ascetical and mystical theology which we have been giving for twenty years at the Angelicum in Rome. In this book we take up in a simpler and higher manner the study of the same subjects that we treated in two other works: Christian Perfection and Contemplation and L’ amour de Dieu et la croix de Jesus. Complying with a request, we offer in this volume our preceding research in the form of a synthesis, in which the different parts mutually balance and illuminate each other. In accordance with advice from various groups, we have eliminated from this exposition discussions to which it is no longer necessary to return. The book thus conceived is accessible to all interior souls.