Res publica Christiana

In medieval and early modern Western political thought, the respublica or res publica Christiana refers to the international community of Christian peoples and states. As a Latin phrase, res publica Christiana combines Christianity with the originally Roman idea of the res publica ("republic" or "commonwealth") to describe this community and its well-being. A single English word with somewhat comparable meaning is Christendom; it is also translated as "the Christian Commonwealth". The concept of a res publica Christiana is first attested in Augustine of Hippo, whose early 5th century work The City of God contrasted the Christian church favourably against the claims of the Roman Empire to constitute a res publica, a republic or commonwealth. He challenged Rome's legitimacy as a state established for the public good on the grounds that its empire had been won by force and not by justice; by contrast, he claimed, the Christian church was a true res publica, founded for the good of humanity. In another work, De opere monachorum, Augustine stated explicitly that "there is one commonwealth of all Christians" ("omnium enim christianorum una respublica est"). Despite Augustine's distinction, in subsequent usage the imperial and ecclesiastical res publica blended together. Thus in the late antique and early medieval period, from the Byzantine Papacy of the 6th century to the turn of the 11th, the papal chancery used the term res publica Christiana mainly to refer to the Christian empire: first the Byzantine Empire in the east, then, from 800, the Carolingian or Holy Roman Empire in the west. The re-establishment of empire in the west subsequently led the popes to use the term in letters of exhortation to Frankish kings who did not necessarily bear the title of emperor themselves, as for example Pope John VIII writing to King Louis the Stammerer in 878 of the "state of the Christian religion and commonwealth" ("statu Christiane religionis ac rei publicae").