Harnack's work is considered by many experts in the field of theology to be unsurpassed. His approach is not meant to prove any set of dogmatic beliefs, as many Christian scholars set out to do, but is one of objectivity. His factual approach is not colored by the bias of trying to save souls or convert readers to the faith. He states early in the book that this is simply an historical approach to the question, What is Christianity? Subjects include The Leading Features of Jesus' Message, God the Father and the Infinite Value of the Human Soul, and large sections on The Gospel in Relation to Certain Problems, and The Gospel in History. He includes a fascinating study on how Roman Catholicism came into power during the 3rd to 6th centuries, and what facets or components of the Christian religion appeared during this time.