In Catholic doctrine, church and state are two different and autonomous institutional subjects, but they are mutually linked. Therefore, a believer, as a citizen, is a subject simultaneously of two legal systems; the state is bound to recognize the confessional dimension of its own members, and the church is called to realize its proper ends within a precise political-social context. The Second Vatican Council (1962–1965) constitutes for the Catholic Church a point of change and renewal. It did not limit itself to affirming the coexistence of the two systems in their independence, but it declared the necessity of a mutual alliance for the good of citizens and believers.
Therefore, the church offers its own contribution to the state, favoring in this way the right to religious liberty; and the state allows the church to establish itself and carry out its proper mission in an institutional form, guaranteeing the protection of the rights of citizens as believers for the free expression of their faith, whether in a private dimension or in an organized form. Vatican II abandons, therefore, the concept of “state religion” in the classic sense of the term, and thus the privilege reserved to one among numerous religious expressions, and opens an authentic collaboration between parties as a prerequisite for the good not only for individual believers and religious organizations, but also for society itself. In particular, religious liberty finds its foundation no longer in the concept of truth (that legitimized the exclusion of other confessions in that they were “not true”), but in the concept of the dignity of the person, which must be protected as such.