On the eighteenth of June, 1452, Pope Nicholas V issued a document called Dum Diversas — meaning “Until Different” — addressed to King Alfonso V of Portugal. The document authorized the Portuguese crown to “attack, conquer, and subjugate Saracens, pagans and other enemies of Christ,” to “reduce their persons to perpetual slavery,” and to “appropriate to themselves and their use” all the lands, property and kingdoms of these peoples. It was, in effect, a global license issued by the highest religious authority in Christendom to one of its most aggressive maritime powers: the right to conquer, enslave and dispossess any human being on earth who was not a Christian.

Three years later, in 1455, Nicholas issued Romanus Pontifex — meaning “The Roman Pontiff” — which extended and elaborated these powers, specifically authorizing Portugal to trade in enslaved Africans and to claim sovereignty over any land it discovered along the African coast. In 1456, Inter Caetera Divinae confirmed these grants. And in 1493, one year after Columbus arrived in the Caribbean, Pope Alexander VI issued a new Inter Caetera dividing the entire non-Christian world between Spain and Portugal along a line of demarcation drawn through the middle of the Atlantic Ocean.

These four documents constitute the Doctrine of Discovery. They are the legal foundation of Atlantic colonialism. Every land seizure, every enslavement, every denial of Indigenous sovereignty in the Americas, Africa, Asia and the Pacific for the next five centuries rested, at its foundation, on these four documents. They were not universally recognized by non-Catholic powers — Protestant England, the Netherlands and France developed their own versions of the doctrine that did not depend on Papal authority but retained the same fundamental claim: that non-Christian peoples had no sovereign rights that Christian powers were bound to respect.

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The Four Papal Bulls — A Close Reading

Dum Diversas of 1452 is the foundational document. Its language is specific and its authorization is comprehensive. The Portuguese are authorized to “invade, search out, capture, vanquish, and subdue all Saracens and pagans whatsoever, and other enemies of Christ wheresoever placed.” The authority to enslave is explicit: “to reduce their persons to perpetual slavery.” The authority to seize property is explicit: “and to take all their possessions and property, and to put them to your use and your successors’ the Kings of Portugal and to convert them to your use and profit.” This is not a military authorization with incidental legal consequences. It is a comprehensive legal framework for dispossession and enslavement, issued with the full authority of the papacy.

Romanus Pontifex of 1455 extended these powers specifically to the African slave trade, granting Portugal “the faculty to invade, conquer, fight, subjugate the Saracens and pagans, and other infidels and enemies of Christ, and wherever established their kingdoms, duchies, counties, principalities, and other dominions, lands, places, villages, camps, and any other possessions, movable and immovable goods found in all these places and to lead their persons in perpetual servitude.” The document also granted Portugal a monopoly over trade and navigation along the African coast — the first legal instrument of what would become the Asiento system of licensed slave trading examined in Chapter Five.

The Inter Caetera of 1493 is the most consequential geopolitically. In this document, Pope Alexander VI drew a line from the North Pole to the South Pole, one hundred leagues west of the Azores, and declared that all lands to the east belonged to Portugal and all lands to the west belonged to Spain — subject to the rights of any Christian prince who had already claimed specific territories. The peoples already living in those lands were legally irrelevant. Their existing sovereignty, governance systems, property rights and community relationships were not factors in the Pope’s calculation. They did not exist, legally, as rights-bearing parties. The land was empty — terra nullius — regardless of how many millions of people lived on it.

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The Valladolid Debate — The Empire Examines Its Own Conscience

In 1550 and 1551, the Spanish Crown convened an extraordinary debate in Valladolid. The question before the assembled theologians and legal scholars was a direct one: did the Spanish have the right to make war on the Indigenous peoples of the Americas before preaching the Gospel to them? Was conquest justified without prior evangelization?

On one side was Juan Ginés de Sepúlveda, the humanist scholar and chaplain to Charles V. His argument drew directly on Aristotle’s theory of natural slavery: the Indigenous peoples of the Americas were natural inferiors, barbarians in the Aristotelian sense, who lacked the rational capacity for self-governance and who benefited from Spanish conquest and Christian civilization. They were, Sepúlveda argued, natural slaves. War against them was not merely permitted but just.

On the other side was Bartolomé de las Casas, the Dominican friar and former slave-owner who had, after witnessing the violence of Spanish colonialism in the Caribbean, dedicated his life to arguing against it. Las Casas rejected the natural slavery argument comprehensively. The Indigenous peoples of the Americas had their own rational faculties, their own governance systems, their own legal and cultural traditions. They were not natural slaves. They were sovereign peoples with rights that the Spanish were bound to respect.

The debate did not produce a winner in any formal sense. No verdict was recorded. But its significance lies in what it revealed: that the legal and theological foundations of the colonial enterprise were recognized, even within the empire itself, as requiring justification. Las Casas’s arguments did not stop the conquest. But they established, within the Catholic legal tradition, a counter-argument that would resurface over and over in the centuries that followed — in the arguments of Maroon treaty negotiators, in the petitions of enslaved people seeking legal recognition, in the advocacy of Indigenous rights lawyers working today under the framework of UNDRIP.

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The Protestant Doctrine of Discovery — The Same Claim, Different Theology

Protestant England, the Netherlands and France did not accept Papal authority over colonial claims. But they did not reject the Doctrine of Discovery. They reformulated it in terms that did not depend on Catholic theology but reached the same conclusion.

The English version, developed through legal cases and colonial charters in the seventeenth century, rested on the concept of vacuum domicilium — empty dwelling. Land that was not being cultivated in the European sense — enclosed, fenced, subject to individual property ownership — was, by English legal definition, empty. The fact that Indigenous peoples hunted, gathered, cultivated, maintained and governed these territories for thousands of years was legally irrelevant. They did not use the land in the way that English property law recognized. Therefore they had no property rights in it.

John Winthrop, the first governor of the Massachusetts Bay Colony, articulated this argument explicitly in 1629. The land of New England was “vacuum domicilium” — legally empty — because the Indigenous inhabitants had not “subdued” it in the English legal sense. The Pilgrim settlers were not displacing rightful owners. They were occupying empty land. The legal architecture was the same as the Papal Bull. The theological vocabulary had changed. The outcome was identical.

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The 2023 Repudiation — And What It Does Not Undo

On March 30, 2023, the Vatican issued a joint statement repudiating the Doctrine of Discovery. The statement acknowledged that the Papal Bulls of the fifteenth century “did not adequately reflect the equal dignity and rights of indigenous peoples” and declared that they “are not part of the teaching of the Catholic Church.” It was a significant acknowledgment — the first formal Vatican repudiation of the documents that had authorized five centuries of colonial dispossession.

But the statement was also carefully limited. It acknowledged that the Papal Bulls were wrong. It did not address the legal consequences of their wrongness. It did not call for the return of lands seized under the Doctrine of Discovery. It did not acknowledge a legal obligation of remediation. It was, in legal terms, a moral acknowledgment without legal consequence — significant as a statement of principle, inadequate as a response to the scale of dispossession the doctrine enabled.

The legal work of dismantling the Doctrine of Discovery’s ongoing effects continues. It continues in the courts where Indigenous nations litigate land rights under treaties that colonial governments have spent three centuries trying to avoid honoring. It continues in the work of the UN Permanent Forum on Indigenous Issues and in the implementation battles over UNDRIP. And it continues in the communities — Maroon, Quilombo, First Nations — that maintained their sovereignty claims through the entire period of colonial suppression and are still asserting them today.