One of the most widely discussed sections of Magnifica Humanitas is Pope Leo XIV’s reflection on whether war can still be considered “just” in the modern age.

In the encyclical, Pope Leo XIV argues that the destructive power of contemporary warfare—especially in the nuclear era, combined with autonomous weapons and advanced military technologies—requires a serious reexamination of traditional just war theory. He writes that the doctrine has too often been invoked to justify conflicts rather than restrain them.

According to the text, the Pope does not completely reject the right of legitimate self-defense. Instead, he stresses that modern warfare has changed the moral landscape so dramatically that older frameworks must be reconsidered in light of present realities. He warns against what he describes as a world increasingly trapped in a “permanent state of belligerence,” where war is again becoming a normal instrument of international politics.

A pᴀssage that has drawn particular attention states:

“The ‘just war’ theory, which has all too often been used to justify any kind of war, is now outdated.”
Rather than relying on military solutions, Pope Leo XIV argues that humanity possesses more effective tools for resolving conflicts, including diplomacy, dialogue, mediation, forgiveness, and international cooperation. He presents peacebuilding not as idealism, but as a moral and practical necessity in an age when modern weapons can inflict catastrophic harm on civilian populations.

The encyclical also connects the question of war to artificial intelligence. Pope Leo XIV warns that autonomous weapons and AI-ᴀssisted warfare risk lowering the moral threshold for violence by distancing decision-makers from the human consequences of conflict. He insists that decisions involving life and death must remain under meaningful human responsibility and ethical accountability.

The document has sparked significant debate among theologians, military ethicists, and Catholic leaders. Some see it as one of the most consequential developments in Catholic teaching on war since the reforms of the Second Vatican Council, while others argue that it represents a continuation of the increasingly strong anti-war emphasis expressed by recent popes.

For many observers, the central message of Magnifica Humanitas is not merely whether a war can be justified. The deeper question posed by Pope Leo XIV is whether humanity, possessing unprecedented technological power and diplomatic tools, can still choose peace before violence becomes the default response to conflict.