European views on colonialism and slavery
Wars of Invasion for the purpose of territorial expansion and enslavement were a feature of Southern, Western and Central European societies going back many centuries. However, the adherence in these areas to a medieval version of Christianity led to the formulation of a right to invade other lands that was bound up with Papal Power. Crusades against Muslim states were sanctioned and encouraged because these were considered a military threat, were non-Christian and included the areas designated as “The Holy Land”. Other non-Christian nations were designated legitimate targets for invasion under the “Doctrine of Discovery” initially detailed in Papal Bulls. Notable are those issued 1452/1455, permitting Portugal to seize land and slaves in West Africa, and the bull Inter Cetera of May 3, 1493 granted Spain the right to conquer the lands that Columbus had already found, as well as any lands which Spain might “discover” in the future.
The Treaty of Tordesillas of 1494 divided lands outside Europe between the Portuguese Empire and the Crown of Castile. A meridian was drawn 370 leagues west of the Cape Verde islands, off the west coast of Africa, about halfway between the Portuguese Cape Verde islands and the Caribbean islands of Cuba and the island of Hispaniola, modern day Haiti and the Dominican Republic. The lands to the west went to Castile because Hispaniola had already been claimed for Castile and León by Christopher Columbus on his first voyage. The lands to the east would belong to Portugal. The later Treaty of Zaragossa similarly defined the Spanish and Portuguese claims in Asia. These treaties did not consider any of the other European powers, which generally ignored the agreement.
The Treaty of Tordesillas declared that only non-Christian lands could be colonized under the “Doctrine of Discovery”, which asserted that title to lands lay with the government whose subjects travelled to and occupied a territory whose inhabitants were not subjects of a European Christian monarch. Despite Papal restrictions, the notion of ‘discovery’ was used to justify enslavement as well as war and territorial seizures. Also, undeterred by sectional differences, both Catholic and Protestant Christian Powers found the doctrine a convenient justification for the expropriation of Indigenous lands. A Massachusetts Bay Colony law of 1633 decreed that “what lands any of the Indians have possessed and improved, by subduing the same they have a just right unto according to that in Genesis“.Therefore, any land not so “improved” could not rightfully be held by the Native Americans, but could be seized by the settlers.
Doctrine of Discovery still in use today
In 2010 a UN study established “that the Doctrine of Discovery has been institutionalized in law and policy, on national and international levels, and lies at the root of the violations of indigenous peoples, human rights, both individual and collective. This has resulted in state claims to, and the mass appropriation of, the lands, territories, and resources of indigenous peoples. Both the Doctrine of Discovery and a holistic structure termed the Framework of Dominance have resulted in centuries of virtually unlimited resource extraction from the traditional territories of indigenous peoples. This, in turn, has resulted in the dispossession and impoverishment of indigenous peoples, and the host of problems that they face today on a daily basis.”The study found not only that USA Supreme Court ruling Johnson & Graham’s Lessee v. M’Intosh in 1823, had used the doctrine to the detriment of the Indigenous Nations of North America, but they also found evidence “demonstrating that the Doctrine of Discovery continues to be treated as valid by the USA Government.”
 Gonnella Frichner, Tonya, 2010, ‘Impact on Indigenous Peoples of the International Legal construct known as the Doctrine of Discovery, which has served as the Foundation of the Violation of their Human Rights‘, New York: UN Economic and Social Council, p.1