To His Eminence Cardinal Peter K.A. Turkson
Chancellor of the Pontifical Academy of Social Sciences

I send warm greetings to you and to all taking part in the International Conference organized by the Academy of Social Sciences and the Peace Research Institute Oslo to commemorate the sixtieth anniversary of the publication of Pacem in Terris, the landmark encyclical of Pope John XXIII.  The Conference is most timely, as our world continues to be in the grip of a third world war fought piecemeal, and, in the tragic case of the conflict in Ukraine, not without the threat of recourse to nuclear weapons.

Indeed, the current moment ominously resembles the period that immediately preceded Pacem in Terris, when in October 1962 the Cuban missile crisis brought the world to the brink of widespread nuclear destruction.  Sadly, in the years that followed that apocalyptic threat, not only has the number and potency of nuclear weapons grown, but other weapon technologies have burgeoned, and even the long-standing consensus to prohibit chemical and biological weapons is coming under stress.  Today, more than ever, we must heed Pope John’s prophetic admonition that, in light of the terrifying destructive force of modern weapons, “relations between States, as between individuals, must be regulated not by armed force, but in accordance with the principles of right reason: the principles, that is, of truth, justice and vigorous and sincere cooperation”. 

In this regard, it is most fitting that this Conference should devote its reflections to those parts of Pacem in Terris that discuss disarmament and the pathways to lasting peace.  It is my hope that your deliberations, as well as analyzing current military and technology-based threats to peace, will include disciplined ethical reflection on the grave risks associated with the continuing possession of nuclear weapons, the urgent need for renewed progress in disarmament, and the development of peace-building initiatives.  I have elsewhere stated my conviction that “the use of atomic energy for purposes of war is immoral, just as the possessing of nuclear weapons is immoral” (Address at the Hiroshima Peace Memorial, 24 November 2019).  It is the responsibility of all of us to keep alive the vision that “a world free of nuclear arms is possible and necessary” (Address to the Diplomatic Corps, 10 January 2022).  Here, the work of the United Nations and related organizations in raising consciousness and promoting adequate regulatory measures remains fundamental.

In a similar vein, concern for the moral implications of nuclear warfare must not be allowed to overshadow the increasingly urgent ethical problems raised by the use in contemporary warfare of so-called “conventional weapons”, which should be used for defensive purposes only and not directed to civilian targets.  It is my hope that sustained reflection on this issue will lead to a consensus that such weapons, with their immense destructive power, will not be employed in a way that foreseeably causes “superfluous injury or unnecessary suffering”, to use the words of the St. Petersburg Declaration.  The humanitarian principles that inspired those words, grounded in the tradition of the ius gentium, remain as valid today as when they were first written, over a hundred and fifty years ago.

Conscious of the important issues under discussion in the Conference, I express my appreciation to the presenters and to those taking part.  I willingly reiterate the prayerful hope expressed by Pope John at the conclusion of his Encyclical that “by God’s power and inspiration, all peoples may embrace each other as brothers and sisters, and that the peace for which they long may ever flourish and reign among them”.  To all I send my blessing.

From the Vatican, 12 September 2023

FRANCIS