This series is a survey of the church's response to the challenge of the twentieh century. One hundred and fifty books by scholars of wide reputation, each an expert in the field he describes, will cover the whole area of modern knowledge in the light of Catholic teaching. Each volume, although a part of the overall encyclopedic structure, is self-contained with its own list of references and biblipography. The series is grouped in sections and the covers of the books in each section are coloured uniformly for easy reference.