Vidkun Quisling, who after World War II was executed as a traitor to his country/Norway, offers an unusual opportunity to reach the deepest layers of a Nazi mind-set, for he was also a closet philosopher. Was Quisling a genius, as some revisionists will have it? What did the original Quisling think? How did he think? A Nazi Interior deals with Quisling’s own all-embracing philosophy, which he called «Universism». The author identifies Quisling’s sources from early Christianity to the twentieth century and analyses his very mode of thought. Barth is the first philosopher to deal with this matter. This book is constructed around twenty-eight basic themes central to Quisling’s thought. Many of the conclusions come as a surprise. The author offers clear surveys of the elements of Quisling’s mind-set and shows the effects of their interaction.