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.

[4] By the 11th century, the term had been generalized through application in different political contexts to mean the totality of Christian states as a community under the leadership of the pope—the primary sense it retained in the Middle Ages from this time on.

It was only in the Renaissance era that the res publica Christiana took on renewed significance: in papal documents, after a period of disuse beginning in the 13th century, the term was revived in the 15th and early 16th centuries by humanist popes such as Pius II, who invoked it in calling for a crusade following the fall of Constantinople to the forces of Mehmed the Conqueror in 1453, and Leo X, likewise concerned in the 1510s to encourage the rulers of Europe to defend Christendom against the Ottoman Turks.

The duc de Sully, chief minister of Henry IV of France at the turn of the 17th century, and his later successor Cardinal Richelieu both sought to realize a form of res publica Christiana: Sully in the form of a proposal for a federal council of Christian states to resolve conflicts in Europe, Richelieu under the label of the "peace of Christendom" (paix de la chrétienté).

[8] As late as 1715, the German polymath Gottfried Wilhelm Leibniz appealed to the concept of a res publica Christiana under the leadership of the pope and emperor as a federative model for European political unity.

One example of subsequent use of the phrase is the 1766 encyclical of Pope Clement XIII, Christianae reipublicae salus [de; it] ("The Welfare of the Christian Commonwealth"), which condemned the "desolation" caused to the res publica by the free circulation of anti-Christian writings and urged Catholic rulers to suppress them.