What is "sacralism"

Sacralism is the confluence of church and state wherein one is called upon to change the other.

Christian sacralism is, according to Verduin, the hybrid product that resulted from the colossal change known as the Constantinian shift that began early in the fourth century AD, when Christianity was granted official tolerance in the Roman Empire by the Emperor Constantine, and was completed by the Emperor Theodosius's declaration in 392 outlawing paganism and making Christianity the official religion of the Empire.

A Latin saying that has often been used to describe the principle of sacralism is cuius regio, eius religio, or "who has region, decides religion." The idea was that the ruler of each individual area would decide the religion of those under his control based upon his own faith.