On June 18, 1452, Pope Nicholas V issued the papal bull Dum Diversas, authorizing King Alfonso V of Portugal to attack, conquer and enslave Saracens, pagans and any other unbelievers, and to seize their lands, property and possessions. Three years later, on January 5, 1455, the same pope issued Romanus Pontifex, which extended this authorization specifically to the West African territories and peoples that Portuguese explorers were encountering, and granted Portugal the exclusive right to trade and colonize in those territories. In 1493, Pope Alexander VI issued Inter Caetera, which divided the non-Christian world between Spain and Portugal along a line drawn through the middle of the Atlantic Ocean.

These three documents — Dum Diversas, Romanus Pontifex, and Inter Caetera — are the legal foundation of European colonialism. They are the documents that established the Doctrine of Discovery: the legal principle that Christian European nations had the right to claim sovereignty over any territory occupied by non-Christian peoples, that the peoples of Africa, the Americas and Asia had no legal right to their land, their freedom or their own governance, and that the Pope had the authority to divide the non-Christian world between the Christian powers of Europe. The Doctrine of Discovery is not ancient history. It was cited by the United States Supreme Court in Johnson v. M’Intosh in 1823 as the legal basis for US land titles. It was cited by the Canadian Supreme Court as recently as 2023. The papal documents that established it have never been formally revoked by the Catholic Church.

The Legal Logic of the Papal Bulls

The legal logic of the Papal Bulls combined Roman legal concepts with Catholic theological doctrine to produce a framework for colonial dispossession that was, within its own terms, internally coherent. The Roman concept of dominium — absolute ownership — required that property be held by legal persons. The Roman concept of persona — legal mask — determined who counted as a legal person. The Catholic elaboration of the Roman legal tradition defined full legal personhood as requiring Christian baptism. Non-Christian peoples were, in this framework, not full legal persons. They could not hold dominium. Their occupation of land did not constitute legal ownership in the sense that Roman law recognized. Terra nullius — empty land — was the legal fiction that expressed this conclusion: the land was legally empty because the people on it did not have legal personhood adequate to establish legal ownership.

The Doctrine of Discovery built on this foundation to authorize the seizure of non-Christian lands by Christian sovereigns. The authorization was not merely moral or political; it was legal. The Papal Bulls were legal documents, issued by the supreme legal authority of the Catholic Church, drawing on the Roman legal tradition that underlay the Church’s own legal system (canon law), and extending that tradition to cover the new situations created by European maritime expansion. The result was a legal framework that, within the terms of the dominant legal tradition of fifteenth-century Europe, provided valid legal title for the seizure of the territories and enslavement of the peoples of Africa, the Americas and Asia.