The relation of religious cult and the state was discussed by the ancient Latin scholar Marcus Terentius Varro, under the term of theologia civilis (lit.
In the Middle East, the majority of states with a predominantly Muslim population have Islam as their official religion, though the degree of religious restrictions on citizens' everyday lives varies by country.
Turkey, which also has Muslim-majority population, became a secular country after Atatürk's Reforms, although unlike the Russian Revolution of the same time period, it did not result in the adoption of state atheism.
It can range from mere endorsement (with or without financial support) with freedom for other faiths to practice, to prohibiting any competing religious body from operating and to persecuting the followers of other sects.
[169][170] Catholic Christianity, as opposed to Arianism and other ideologies deemed heretical, was declared to be the state religion of the Roman Empire on 27 February 380[175] by the decree De fide catolica of Emperor Theodosius I.
This sort of Confucianism continued to be regarded by the emperors, with a few notable exceptions, as a form of state religion from this time until the collapse of the Chinese monarchy in 1912.
Their official favoring of Islam as the state religion coincided with a marked attempt to bring the regime closer to the non-Mongol majority of the regions they ruled.
In Ilkhanate, Christian and Jewish subjects lost their equal status with Muslims and again had to pay the poll tax; Buddhists had the starker choice of conversion or expulsion.