This is a stimulating, scholarly analysis of ""the urban scene"" and ""the roles (in it) of Christian lay leaders, families, parishes, communities and movements"" by one who is an expert on housing and racial relations and a member of the Committee on Human Relations for the City of Philadelphia. The resources of theology, philosophy, sociology, psychology and personal observation are utilized here to help the Christian to realize the character and religious implications of the urban environment in which the majority of today's Catholics live. The approach is radical--in the philosophical sense of the term--constructively critical and highly practical. A program of ""study, organization, education and social action of Christians in urban affairs"" is suggested. An Appendix describes the ancient, medieval, renaissance and industrial cities of the past, pointing up the unique character of today's technological city, that challenges Catholics, both clerical and lay, in ways they often hardly suspect. This book fills a definite need that should be felt by every Catholic whose life affects and is affected by the predominantly pagan civilization and culture of the modern city in which he dwells.