This article notes that the Church was intervening against slavery even before the arrival of Europeans in the New World.
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From the article:
THE POPES AND SLAVERY: SETTING THE RECORD STRAIGHT
Fr. Joel S. Panzer
"From 1435 to 1890, we have numerous bulls and encyclicals from several popes written to many bishops and the whole Christian faithful condemning both slavery and the slave trade. The very existence of these many papal teachings during this particular period of history is a strong indication that from the viewpoint of the Magisterium, there must have developed a moral problem of a different sort than any previously encountered. In this article I will address three—from many more—of the responses of the papal Magisterium to the widespread enslavement that accompanied the Age of Discovery and beyond.
Eugene IV: , 1435
On January 13, 1435, Eugene IV issued from Florence the bull . Sent to Bishop Ferdinand, located at Rubicon on the island of Lanzarote, this bull condemned the enslavement of the black natives of the newly colonized Canary Islands off the coast of Africa. The Pope stated that after being converted to the faith or promised baptism, many of the inhabitants were taken from their homes and enslaved:
“They have deprived the natives of their property or turned it to their own use, and have subjected some of the inhabitants of said islands to perpetual slavery (), sold them to other persons and committed other various illicit and evil deeds against them… Therefore We … exhort, through the sprinkling of the Blood of Jesus Christ shed for their sins, one and all, temporal princes, lords, captains, armed men, barons, soldiers, nobles, communities and all others of every kind among the Christian faithful of whatever state, grade or condition, that they themselves desist from the aforementioned deeds, cause those subject to them to desist from them, and restrain them rigorously. And no less do We order and command all and each of the faithful of each sex that, within the space of fifteen days of the publication of these letters in the place where they live, that they restore to their pristine liberty all and each person of either sex who were once residents of said Canary Islands … who have been made subject to slavery (). These people are to be totally and perpetually free and are to be let go without the exaction or reception of any money.”
The date of this Bull, 1435, is very significant. Nearly 60 years before the Europeans were to find the New World, we already had the papal condemnation of slavery as soon as this crime was discovered in one of the first of the Portuguese geographical discoveries.
Eugene IV was clear in his intentions both to condemn the enslavement of the residents of the Canary Islands, and to demand correction of the injustice within 15 days. Those who did not restore the enslaved to their liberty in that time were to incur the sentence of excommunication ipso facto.
With , Eugene was clearly intending to condemn the enslavement of the people of the Canaries and, in no uncertain terms, to inform the faithful that what was being condemned was what we would classify as gravely wrong. Thus, the unjust slavery that had begun in the newly found territories was condemned, condemned as soon as it was discovered, and condemned in the strongest of terms.