In his infamous tome, Hitler categorized human beings by their physical attributes, claiming German or Nordic Aryans were at the top of the hierarchy while assigning the bottom orders to Jews and Romani. Hitler claimed that dominated people benefit by learning from superior Aryans and said the Jews were conspiring to keep this "master race" from rightfully ruling the world by diluting its racial and cultural purity and exhorting Aryans to believe in equality rather than superiority and inferiority. Within "Mein Kampf", Hitler describes a struggle for world domination, an ongoing racial, cultural and political battle between Aryans and Jews, the necessary racial purification of the German people and the need for German imperial expansion and colonisation eastwards. According to Hitler and other pan-German thinkers, Germany needed to obtain additional living space or "Lebensraum" which would properly nurture the "historic destiny" of the German people. This was a key idea he made central in his foreign policy. Hitler wrote in "Mein Kampf" of his hatred towards what he believed were the world's twin evils, namely communism and Judaism. He said his aim was to eradicate both from Germany and moreover stressed his intention to unite all Germans in the process of destroying them.