What do we really know about the sources of Adolf Hitler's anti-Semitism? What led him to become such a genocidal anti-Semite? It is often said that the strongly anti-Semitic atmosphere in pre-war Vienna, in which Hitler failed to achieve his dream of becoming an artist, was when his hatred of the Jews first began to stir. We also often read that such feelings were compounded by the so-called stab in the back' by Jewish-Marxists at the end of the First World War, which led to Germany's humiliating capitulation. The Darwinian science of natural selection is often included in the debate as well, which to Hitler meant keeping the Germanic race pure' and untainted by the inferior' Jews. However, as Peter den Hertog sets out in this book, such external, cultural and environmental factors were also experienced by most of Hitler's contemporaries, and they did not all turn into rabid Jew-haters. In this study, the author investigates what we do know about the roots of the German leader's anti-Semitism. He also takes the significant step of mapping out what we do not know in detail. This allows the reader to understand which information needs to be looked for in the search for a complete explanation. Historians will be historians and so have their own way of looking at the world. This fails to provide us with complete clarity in this matter. That is why this study also employs insights from Psychology, Psychiatry and Forensic Psychiatry. Readers even take a trip 65 million years back in time to the field of Evolutionary Psychology. The author reveals how Hitler was a man with highly paranoid traits. The causes of this paranoia are clarified for the first time and its connection to Hitler's anti-Semitism is explained in depth. The author also explores, and answers, whether the F hrer gave one specific instruction ordering the elimination of Europe's Jews, and, if so, when this took place. Peter den Hertog is able to provide an all-encompassing explanation for Hitler's anti-Semitism by combining insights from many different disciplines. He also succeeds in clarifying how Hitler's own particular brand of anti-Semitism could lead the way to the Holocaust.