Isabel Wilkerson emphasizes how caste is both constructed and perpetuated. While she focuses on the United States, she draws on ideas and practices from other countries and regions. One of the key themes she addresses in Caste is the persistence of caste. Rather than looking at a caste system as an aberration that can be easily changed, she demonstrates that caste is deeply entrenched in the American way of life. Another closely related theme is the combination of race and class in caste. Not only is racism at the center of the American caste system, it operates in tandem with class. This intersection serves to keep many economic opportunities out of the reach of people of color.
In emphasizing the self-perpetuating character of caste in the United States, Wilkerson delves back into American and European history. She shows how racism contributed to the establishment and continuation of slavery in the colonies and the independent republic. Ongoing disenfranchisement and discrimination served to keep most African Americans and other people of color from having the upward mobility available to white Americans. Wilkerson takes issue with the ideology of individual self-improvement as the primary means to achieving the American Dream. Instead, she reveals how numerous legal and social barriers to leveling the playing field have contributed to keeping in place a rigid and discriminatory system.