From the foreword:
How did denominations spring up when there was only one church in the New Testament? World religions have their roots in real people and beliefs that date back to the early Bible. Sometimes they borrow from the other religions as Keith traces these facts for the reader. Sometimes they borrow from the Bible so that the new religion has similarities with the Truth. They are always perversions of the true religion of Adam and Noah, of the faithful people of Seth and Shem, of the truth spoken by Moses and the Prophets, and lastly, of Christ and the Apostles.
In The Devils’ Door, Keith has sought to answer the when, where, how, and with whom Pagan deities arose. In this book, he takes a closer look at the people who descended from Seth and Noah and explains how nations sprung up from them with the peculiar religion systems that came to characterize them. The Babylonians, the Egyptians, the Assyrians, Canaanites and others are traceable all the way back to Noah. Keith explores what happened to those people after the worldwide flood.
In The Devils’ Door, Keith sets out to show that the devils’ door was a real architectural item in many pre-reformation churches. The existence of such a thing illustrates how men denominated by incorporating human religious systems into the Christianity. The result was a perversion of Christianity.