Pope Alexander IV passes the papal bull (an edict issued by the pope) Inter Caetera, which asserts that Spain has exclusive rights to all of the territory west of the Azores and Cape Verde Islands in the mid-Atlantic Ocean. Inter Caetera is the first papal ruling to link "exploration" and colonization to Christianity and conversion.

Alexander asserts that: “in our times especially the Catholic faith and the Christian religion be exalted and be everywhere increased and spread, that the health of souls be cared for and that barbarous nations be overthrown and brought to the faith itself.” The pope's claims are based on the Catholic concept of terra nullius or empty land, which is the idea that if land is "empty," it is open to the spread of the Christianity faith.