6th January 2015. Retrieved 11-08-2015.</ref> The practice of religion was tightly controlled in dynastic times and it is also tightly controlled today. Chinese who are over the age of 18 are only permitted to join officially sanctioned Christian groups which are registered with the government-sanctioned Catholic Patriotic Church, the China Christian Council and the Protestant Three-Self Church. On the other hand, many Christians who practice Christianity are members of informal networks and unregistered congregations, these congregations are frequently described as house churches or underground churches, the proliferation of which began in the 1950s when many Chinese Protestants and Catholics rejected the state-controlled structures which were purported to represent them. Members of such groups are said to represent the "silent majority" of Chinese Christians and they also represent many diverse theological traditions. Terminology There are various terms which are used for God in the Chinese language, the most prevalent of them is Shangdi (, literally, the "Highest Emperor"), commonly used by both Protestants and non-Christians, and Tianzhu (, literally, the "Lord of Heaven"), which is most commonly used by Catholics. Shen (), which is also widely used by Chinese Protestants, defines the gods or the generative powers of nature in Chinese traditional religions. Historically, Christians have also adopted a variety of terms from the Chinese classics as references to God, for example, the Ruler () and the Creator (). Terms for Christianity in Chinese include: "Protestantism" (); "Catholicism" (); and Eastern Orthodox Christians (). The whole of Orthodox Christianity is named Zhèng jiào (). Christians in China are referred to as "Christ followers/believers" () or "Christ religion followers/believers" (). History Pre-modern history Earliest documented period The Christian apologist Arnobius (died c. AD 330) claimed in his work Against the Heathen: Book II, that Christianity had reached the land of Seres (an old Roman name for northern China) saying "For the deeds can be reckoned up and numbered which have been done in India, among the Seres, Persians, and Medes; in Arabia, Egypt, in Asia, Syria; among the Galatians, Parthians, Phrygians; in Achaia, Macedonia, Epirus; in all islands and provinces on which the rising and setting sun shines; in Rome herself, finally, the mistress of the world, in which, although men are busied with the practices introduced by king Numa, and the superstitious observances of antiquity, they have nevertheless hastened to give up their fathers' mode of life, and attach themselves to