According to Arendt, racism and antisemitism are ideologies i.e., ideas that provide the foundation for political and economic systems. Racism differs from what she calls “race-thinking” in that race-thinking is a set of opinions. Racism is more dangerous because it has an infectious quality and can be weaponized by totalitarian movements. In a similar way, antisemitism differs from social discrimination or the hatred of Jews; rather, antisemitism seeks to eradicate the Jewish people from the world for political ends. She states that antisemitism is a pre-cursor to totalitarianism, and its connection to totalitarianism has to do with its effectiveness in mobilizing sympathizers. Political antisemitism and social discrimination create a foundation upon which imperialists and totalitarian movements can build.

Racism is first seen as a weapon during the rise of the imperialist age. It became a handy way for white imperialists to justify their actions in the countries they colonized. Imperialists viewed themselves as superior and their colonized subjects as inferior. For example, the Boers perceived themselves to be a chosen people and used their supposed inferiority of African tribes to justify their brutal actions.  Arendt suggests that this idea of power and weakness is at the heart of many ideologies, including Darwinism.