Webster’s New International Dictionary of the English Language, published in 1923, states, under “Family of Nations”: “—f. of nations. Internat. Law, an aggregate of states, which, as a result of their antecedents, have inherited a common civilization, and are at a similar level of moral and political opinions. ‘The term may be said to include the Christian nations of Europe and their offshoots in America, with the addition of the Ottoman Empire, which was declared by the Treaty of Paris of 1856 to be admitted to the ‘concert of Europeen’ [sic] (c.f. CONCERT OF EUROPE). Within this charmed circle, to which Japan also has now established her claim to be admitted, all states, according to the theory of international law are equal. Outside of it no state, be it as powerful and civilized as China or Persia, can be regarded as a normal international person.” Thus, it was as of the 1856 Treaty of Paris that a transition occurred whereby a non‐Christian state was admitted into the Christian Family of Nations.
This is when a shift away from the specific term “Christendom” began. It would be a serious mistake to conclude that such a shift in terminology erased the centuries of conceptual development that had taken place in the context of Western Christenedom. See Johnson v. M’Intosh 21 U.S. 543 (1823) The English possessions in America were not claimed by right of conquest, but by right of discovery. For according to the principles of international law as understood by the then civilized powers of Europe, the Indian tribes in the new world were regarded as mere temporary occupants of the soil, and the absolute rights of property and dominion were held to belong to the European nation by which any particular portion of the country was first discovered. Whatever forbearance may have been sometimes practiced towards the unfortunate aborigines, either from humanity or policy, yet the territory they occupied was disposed of by the governments of Europe at their pleasure, as if it had been found without inhabitants. The grant to the Duke of York therefore was not of lands won by the sword; nor were the government or laws he was authorized to establish intended for a conquered people. See Martin v. Waddell 41 U.S. 367 (1842)
“Sublimis Deus (English: The sublime God; erroneously cited as Sublimus Dei) is a papal encyclical promulgated by Pope Paul III on June 2, 1537, which forbids the enslavement of the indigenous peoples of the Americas (called Indians of the West and the South) and all other people. It goes on to state that the Indians are fully rational human beings who have rights to freedom and private property, even if they are heathen. It strengthens the recent decree issued by Charles V of Spain in 1530 in which the King prohibited the enslavement of Indians. Another related document is the ecclesiastical letter Pastorale officium, issued May 29, 1537, and usually seen as a companion document to Sublimis Deus.”