The massive inequalities of second-wave (classical) civilizations was accepted because of the philosophical religious systems. These systems, which included Greek rationalism, Hindu faith, and Confucian philosophy, supported inequality.
In China, Confucianism was used to justify the class system and patriarchy. Also, Aristotle developed the notion that some people were "slaves by nature" and should be enslaved for their own good and for that of the larger society.
Finally, the social inequity was both accepted and resisted in classical civilizations. Some evidence supporting this statement is the fact that people who disagree with Confucianism fought back with Daoism and the fact that strong states like China served to strengthen social inequality.
