From The New York Times:
It isn’t every day that a pope calls for an overhaul of a more than 1,000-year-old teaching of the Catholic Church, but that’s exactly what Pope Leo XIV did last month. In his inaugural encyclical, “Magnifica Humanitas,” which was mainly an exploration of how to protect human dignity in the age of artificial intelligence, Leo devoted a brief but critical passage to just war theory.
In a break with a foundational principle of Catholic thought on conflict, Leo called the theory “outdated” and made it clear that the teaching has been twisted to justify wars for decades, most recently the war in Iran. It is about time for the change. Just war theory holds that wars must meet strict conditions: They should be in self-defense, and only if alternatives have been exhausted; the use of force should be proportional; there should be a likelihood of success and the threat should be imminent. Since World War II at least, several popes have criticized world leaders for using the theory as a fig leaf. Just war theory was largely developed by St. Augustine in the 5th century and elaborated by St. Thomas Aquinas in the 13th century. For an institution that is averse to change, the idea that anyone, even a pope, would rewrite the teaching of a revered saint might seem to some to be unorthodox, even radical. Yet who better suited to overhaul a major teaching of St. Augustine than this pope, a former head of the religious order named for Augustine, who was taught by Augustinians starting as a teenager and wrote his dissertation on the order’s governance?