What basic beliefs about the world and human beings underpin these jim crow practices?

The idea behind Jim Crow was to keep African Americans oppressed. The idea behind much of this thought and belief system is one that there are some races that are superior and other that are inferior. Some, pre-Civil War, pointed to the Bible and some of the passages that described the enslaving of people with "dark skin". The idea shifted from enslavement to keeping a type of caste system.