For nearly two thousand years, popes have communicated to the world primarily through their letters. In the pre-modern world, the papal chancery turned out tens of thousands of letters a year. On occasion, a letter dealt with broad concerns and was intended to circulate through the churches of a given region. Such letters became known as encyclicals. In the modern period, papal encyclicals have become the primary medium through which the papacy exercises its teaching office. Through them, the popes address theological topics of especially timely concern, applying Christian doctrine to the immediate circumstances of the day.
These encyclicals are a testament to their times. Written during the turbulent 1950s and 1960s, they demonstrate Blessed Pope John XXIII’s commitment to bringing the Gospel to humankind. In Pacem in Terris (Peace on Earth), the first papal encyclical ever addressed not just to the Catholic faithful but “all Men of Good Will,” Pope John XXIII outlines the requirements for basic human rights, saying “Man has the right to live. He has the right to bodily integrity and to the means necessary for the proper development of life. . .” He continues by listing economic, political, immigration, vocational, and religious freedoms that must exist where they are able (e.g. first-world countries). This encyclical, perhaps more than any other pre-Vatican II papal writing, has begun the foundation for the modern Catholic teaching on human rights, freedoms, and responsibilities.