What Pope Leo thinks about just war theory, historic Church apology for slavery

In his first encyclical, Pope Leo XIV used a sweeping reflection on artificial intelligence to question whether the Catholic Church’s centuries-old “just war” framework remains valid in modern warfare and to ask pardon for the church’s role in slavery.

Pope Leo addressed the Catholic Church’s participation in the “scourge of slavery,” in broader terms than many of his predecessors. Previous popes have apologised for more specific instances like Christian involvement in the transatlantic slave trade, but Pope Leo appeared to frame the church’s responsibility more institutionally.

“It is impossible not to feel deep sorrow when contemplating the immense suffering and humiliation endured by so many in stark contrast to their immeasurable dignity as persons infinitely loved by the Lord,” he wrote. “For this, in the name of the church, I sincerely ask for pardon.”

The pope’s comments immediately drew attention because both subjects, just war theory and institutional responsibility for slavery, are novel approaches.

The pope’s 82-page encyclical, Magnifica Humanitas (“Magnificent Humanity”), primarily focuses on the ethical development of artificial intelligence and the dangers posed by autonomous weapons, concentrated technological power and the erosion of human dignity.

But within the document, Pope Leo also makes several broader interventions on war, violence and historical injustice. In discussing such topics, he questioned the of the Catholic teach of “just war” theory in modern warfare, and wrote about slavery in an unprecedented way.