The date when this book was written was the exact tike when "science" started turning what was known for millennia as demonic possession into a psychological illness. They even invented new medical jargon to make it sound more scientific. What's interesting is the occult revival of that time was seeking a dissolving of the core ego (personality) and a replacement by a new and separate ego or personality. Funny how the occult doctrines of spiritism and science lined up perfectly and at the exact same time. Its was the attempt of science to plaster a scientific explanation on the many things they were seeing and couldn't explain.