This book is the product of more than twenty years of research on the anthropology of the Christian vocation. This research was carried out by following, over a period of several years, some hundreds of candidates to the priesthood or the religious life, and also lay college-students, in the USA. This is the second volume of an interdisciplinary study. As such, it has its roots in both philosophy and theology, as explained in the first volume. The more important points of its philosophical and theological foundation find repeated and convergent confirmation in the research-findings and predictions (both statistical and existential) presented in this second volume. In this book, various aspects of the Christian vocation are analyzed; for example, the three dimensions or habitual dispositions underlying this vocation, the intrapsychic factors which seem important for the beginning of vocation, perseverance growth in the internalization or assimilation of vocational values, vocationals crises, the influence of formation on the potentiality of internalization, and the influence of different vocational environments on this potentiality. Each aspects of vocation analyzed in this book is followed by pastoral apllications, often related to the teachings of the Second Vatican Council.