In the 19th century in many Western states, the close relationship between Church and State came to an end and the Roman Catholic Church developed into a major and active player on social and educational level in society separate from the State.
This was due, on the one hand, to the constitutional changes in the Western states from the end of the 18th century, which led to the gradual introduction of the formal principle of separation of Church and State. On the other hand, it was a result of the search for a new position of the Roman Catholic Church in society that also influenced the theological reflection of the Church on society.
The ecclesiastical reflection on the ideal relationship between Church and State took shape in the course of this process in the Ius Publicum Ecclesiasticum. The ecclesiastical view on the relationship between believers/citizens, society and State simultaneously took shape in Catholic social doctrine, which today still offers a model for modern society. In Catholic social doctrine, the believer/citizen is the connecting element between Church and State in a secular society. The ‘state doctrine’ of the Catholic Church is presented in Catholic social doctrine as an ideal image of the democratic constitutional state in which man is central and forms the central link between Church, society and secular State.