Here is an attempt to tell in brief compass the history of Christianity. Christianity is usually called a religion. As a religion it has had a wider geographic spread and is more deeply rooted among more peoples than any other religion in the history of mankind. Both that spread and that rootage have been mounting in the past 150 years and especially in the present century. The history of Christianity, therefore, must be of concern to all who are interested in the record of man and particularly to all who seek to understand the contemporary human scene. - Preface.