Legitimate defense does not justify an arms race

Before the General Assembly of the United Nations, gathered in New York on 26 September for the opening of its eighty-first session, Cardinal Pietro Parolin, Secretary of State of the Holy See, recalled that every people has the right to provide for its own defense, but that this right cannot become the pretext for an arms race, particularly by means of nuclear weapons and autonomous systems.

The doctrine is not born from this podium. The fifth commandment forbids murder, not every act of taking life: the Catechism of the Council of Trent, expounding « Thou shalt not kill », enumerates the cases in which putting to death is not a crime, among them the just war and the defense of one's own existence. Legitimate defense is therefore a true right.

But the same tradition binds it: war is lawful only for a just cause, decided by legitimate authority and waged with a right intention, according to the three conditions of Saint Thomas Aquinas; and it never authorizes the deliberate slaughter of the innocent. The very end of war is peace, that « tranquillity of order » of which Saint Augustine speaks. When the power of destruction escapes entirely from man's control, Pius XII taught that its use must be rejected. « Nothing is lost with peace; everything may be lost with war », warned this pontiff on the eve of the last world conflict.

This is the ground the Secretary of State's intervention covers. « No true peace is possible without genuine common resolve for disarmament; the legitimate right of every people to provide for its own defense must not degenerate into a race to massive rearmament », he declared, naming nuclear weapons and autonomous weapons. He placed his words under a recent encyclical of the reigning pontiff, calling for a passage from a « culture of power » to a « culture of negotiation »: a text posterior to the council, which we report as the fact of a speech and not as the measure of truth.

The day before, on 25 September, at a dinner held on the margins of the UN week, the cardinal had traced the fragmentation of the world back to the forgetting of what the human person is, invoking the encyclical Rerum Novarum of Leo XIII and Saint Augustine, and exhorting his hearers: « In a world connected online and disconnected offline, be people of presence. In a world asking whether we can remain human, answer with the witness of your lives. »

Sources. Catechism of the Council of Trent (1566), exposition of the fifth commandment; Saint Thomas Aquinas, Summa Theologica, IIa-IIae, q. 40, on the conditions of the just war; Saint Augustine, The City of God, XIX, on peace as the tranquillity of order; Pius XII, radio message of 24 August 1939, and allocution of 30 September 1954 on weapons whose effects escape man's control.