Deep thanks are extended to the authors of these studies whose pioneering efforts have opened new paths and greatly enriched human vision in our times. It is no exaggeration to say that their work is at the center of the efforts of persons and peoples to discover today what it means to be human.

Particular gratitude is due also to B. Kennedy, Linda Perez, Carol Dupré, Nancy Graham and Hu Yeping for their work in bringing this manuscript into final form.