On 9 April 1963, on live television, John XXIII signed his last encyclical, entirely dedicated to the theme of peace, which will bear the date 11 April.

We could consider this document his testament, left to the Church which he had gathered in the Council on October 11, 1962 and to all the men and women of good will, whom he had thought of in averting a positive solution to the Cuban crisis.

His speech was accompanied by the favor of providence and the common sense of those who governed the fate of the superpowers of the USA and the USSR.

One gesture concerned Pope Roncalli's sensibility in the aftermath of the publication of the encyclical Mater et Magistra (July 1961): the construction of the Berlin Wall.

His heart as a true Shepherd of all humanity, as he believed himself to be and to operate, led him to remind the Church and the world of the importance of building consciences that look to peace and work in every field and sector so that this can be pursued, together with the fight against hunger, as a primary good for all humanity.

Already Benedict XV, at the time of the First World War, had stigmatized armed conflict as a "useless massacre" and Pius XII had asked the world to reflect that "with war all is lost".

Pope John with the Council had indicated to the Catholic Church the path of fidelity to the "depositum fidei", with great attention to those signs of the times to be grasped and "brought" to offer humanity the maternal face of the Church which, by mandate of Christ, must offer humanity and every man mercy and forgiveness.

If the encyclical Pacem in terris, as it appears at first glance, is entirely dedicated to the theme of non-aggression and the building of paths of peace, it should however be emphasized that this document of the papal magisterium is also the exaltation of the human person , which has always been the motive for every document of the Church's social doctrine starting with Leo XIII's Rerum Novarum. It is to the person that the Church looks and emphasizes rights and duties, not to this or that category to which the person is linked or inserted.

Christian redemption itself is addressed to man impoverished by sin and offers him the work of the Incarnate Word so that, welcomed into the freedom of the person, he may give redemption and salvation.

Sixty years after the Johannine encyclical, after the last documents concerning the social attention of the Christian, such as Pacem in Terris, Benedict XVI's Caritas in veritate and Pope Bergoglio's Laudato si', the Catholic Church, through the constant and almost daily calls by Pope Francis to respect the human person, for peace between peoples and for the protection of creation, calls all of humanity to consider the prophetic words of Paul VI to the UN: "If humanity does not put an end to war, it will be the war that will put an end to humanity”.

Unfortunately today there are too many wars waged in the world and there is the great danger of becoming accustomed to a situation of conflict, placing everything in an armed competition which will certainly bring ruin, but which will be able to contribute very little to peace.

One of the ways John XXIII practised to avert the crisis in Cuba was that of "personal and effective negotiations" between the powerful of the time. Therefore, to eradicate conflicts it is necessary to overcome the adage: "If you want peace, prepare for war", but it is necessary to recall that if you want peace, you need to educate to peace at every level "opportune et importune".

In this time of great concern for humanity, it seems more than ever necessary to revisit John XXIII's encyclical to grasp its spirit and the urgency of working with concrete conviction, as did Paul VI who instituted the day of reflection for peace and which indicated in development the true name of a just and lasting peace between "the peoples of opulence and those of poverty".

The encyclical Pacem in Terris is a great gift for believers and non-believers who truly want to choose to do their utmost in favor of the promotion of the human person and of harmony in solidarity and justice of the entire human family, beyond differences of any kind and degree social, in the search for a peace that gives dignity to man and protects the whole of creation.