The book is intended primarily for students of Social Science who accept the Church's teaching. Its main purpose is to summarise and present in a consecutive and more or less scientific form the main elements of the teachings of the Roman Pontiffs (especially Leo XIII and our present Holy Father Pius XI), the Catholic Bishops and the standard Catholic authors on questions connected with social organisation and public life, including such topics as personal rights and duties, the privileges and position of the family in the social organism, the interrelations of capital and labour, the place of religion in public life, education, the functions of the State, its constitution, laws and administration, the due interrelations of its component parts with one another, its relations with the Church, etc. Here and there in the book will be found suggestions borrowed mostly from approved Catholic writers, as to practical means of realising Christian princip1es and ideals in social and civic organisation. The principal non-Catholic theories on the subjects discussed, and modern non-Christian tendencies and movements are also dealt with; and tho well-being of the people under the Christian regime as illustrated from history is compared with their position in the non-Christian State. Following the precedent of French, American and English writers on the same subjects, the author has striven to give special prominence to those aspects of the questions dealt with, which seem to have special importance in his own country; and he naturally chooses bis illustrations of principles and their application from existing circumstances in Ireland, the country with which he is most familiar. The main portions of the work, however, apply to all countries. Hence the writer hopes that the book may prove useful even to non-Irish readers. On that account he has relegated to Appendices the treatment of certain aspects of the social question which are rooted in historical causes peculiar to Ireland. The writer wishes to thank very sincerely the kind friends whose invaluable assistance and patient collaboration have enabled him to complete much sooner than he could otherwise have hoped the tedious work of preparing the book for publication. He wishes also to thank those other friends whose helpful advice and friendly criticism have assisted him very much in the work of revision. Finally, he gladly acknowledges the great assistance he has received from the discussions carried on during the past five years at the meetings of An Rioghacht. These discussions have served especially to throw light on many practical questions, and have given the writer an insight into certain aspects of his subject with which he would be otherwise unacquainted.