Under the Zhou dynasty China made many technological advances and grew in population. The later Qin and Han dynasties set up powerful central governments that brought stability, expanded Chinese territory, and increased foreign trade. Two notable achievements were the building of the Great Wall to protect against invaders from the north and the creation of a civil-service system in which officials were appointed on the basis of examinations. Two major philosophies developed: Confucianism, which stressed basic moral rules in human relationships and the ideal of a courteous, well-educated individual, and Daoism, which emphasized living in harmony with nature. Chinese society consisted of landowners, peasants, and merchants. The family unit functioned as an economic unit. The Chinese also produced the first printed book and developed paper and gunpowder.