In the Western Zhou Dynasty, social classes consisted of the sovereign(tian-zi), dukes(zhu-hou), ministers(qing), bureaucrats(da-fu) and scholar-officials(shi), etc., among which scholar-officials in lower positions and those classes lower than scholar-officials belonged to the middle and lower classes. Although the Western Zhou Dynasty adopted the hereditary system that resisted social mobility, the practice that rulers promoted the capable and virtuous and put them in important positions had provided space for upward mobility in ways of being recommended, performing outstandingly in school or shooting ritual, gaining military merits and self recommendation. Some other people in the middle and lower classes could also have opportunities to move upward due to loyal execution of orders, marriage with aristocrats, and so on.