Papal Bull Dum Diversas
18 June, 1452

Pope Nicholas V issued the papal bull Dum Diversas on 18 June, 1452. It authorised Alfonso V of Portugal to reduce any “Saracens (Muslims) and pagans and any other unbelievers” to perpetual slavery. This facilitated the Portuguese slave trade from West Africa.

The same pope wrote the bull Romanus Pontifex on January 5, 1455 to the same Alfonso. As a follow-up to the Dum diversas, it extended to the Catholic nations of Europe dominion over discovered lands during the Age of Discovery. Along with sanctifying the seizure of non-Christian lands, it encouraged the enslavement of native, non-Christian peoples in Africa and the New World.

“We weighing all and singular the premises with due meditation, and noting that since we had formerly by other letters of ours granted among other things free and ample faculty to the aforesaid King Alfonso -- to invade, search out, capture, vanquish, and subdue all Saracens and pagans whatsoever, and other enemies of Christ wheresoever placed, and the kingdoms, dukedoms, principalities, dominions, possessions, and all movable and immovable goods whatsoever held and possessed by them and to reduce their persons to perpetual slavery, and to apply and appropriate to himself and his successors the kingdoms, dukedoms, counties, principalities, dominions, possessions, and goods, and to convert them to his and their use and profit -- by having secured the said faculty, the said King Alfonso, or, by his authority, the aforesaid infante, justly and lawfully has acquired and possessed, and doth possess, these islands, lands, harbors, and seas, and they do of right belong and pertain to the said King Alfonso and his successors”.

In 1493 Alexander VI issued the bull Inter Caetera stating one Christian nation did not have the right to establish dominion over lands previously dominated by another Christian nation, thus establishing the Law of Nations.

Together, the Dum Diversas, the Romanus Pontifex and the Inter Caetera came to serve as the basis and justification for the Doctrine of Discovery, the global slave-trade of the 15th and 16th centuries, and the Age of Imperialism.