Vitoria – who was born at the end of the 15th century in northern Spain and entered the Dominican order as a young man – taught at a time when some of Spain’s intellectuals were experiencing a crisis of conscience, brought about by their country’s discovery of the New World.

In 1492, Christopher Columbus completed his first voyage to the Americas. Legions of Spanish soldiers, or conquistadores, followed in his wake. What followed was subsquently described by another Dominican of that time, Bartolome de las Casas, as “the wholesale slaughter” of innocent people.

Las Casas, a contemporary of Vitoria’s, came to be called the Apostle to the Indians. He travelled to the Americas as a missionary and lived there among the native peoples, becoming an ardent champion of their rights and recording their suffering in A Short Account of the Destruction of the Indies. In it, he wrote: “All the peoples of the world are humans and there is only one definition of all humans and of each one, that is that they are rational...Thus all the races of humankind are one.”

Back in Spain, in the University of Salamanca where he was elected to head the teaching of theology, Vitoria began building the intellectual backbone to support Las Casas’ vision of humanity as one.

In 1532, Vitoria launched a series of lectures that laid down the principles of how nations should deal with each other, using the context of Spain’s conquest of the Americas. Published posthumously after his death in 1546, as Relección de los Indios, or Readings on the Indians and on the Law of War, the lectures were rooted in this one basic idea: that all men are created free and equal.

Every man, having been made in the image of God and endowed with a rational nature, enjoys certain rights, to life, property, liberty and dignity. Drawing from St Thomas Aquinas’ writings on natural law, Vitoria argued that man is the image of God by his rational nature, not by grace. Therefore, those rights which are natural to man cannot be taken away or given to him on account of sin.