The idea for this book grew out of a NATO Advanced Research Workshop held at the Catholic University at Leuven, Belgium. We are grateful to NATO for support in conducting this workshop and for support in the preparation of this book. We are particularly grateful for their emphasis on designing the workshop to build collegiality. They suggested that we hold the meeting in a small town and that we organize evening activities to keep the group together and to promote informal and extended discussions. What sage advice. The excitement grew over the three days as we shared understandings and...