The words and deeds of Pope Pecci revealed his deep religiosity; and this had a correspondence in his magisterium: Among his many encyclicals and apostolic letters, like the string of a necklace, there are those of a specifically spiritual character, dedicated above all to the growth of Marian devotion, especially through the rosary. It is a real “catechesis” that stretches from the beginning to the end of the 25 years of his pontificate.
But we also have the documents on Christ the Redeemer, on the Holy Spirit, on consecration to the Sacred Heart, on devotion to St. Joseph, on St. Francis of Assisi. Leo XIII was especially close to the Franciscan family and he himself belonged to the Third Order. I like to consider all of these different elements as various facets of a single reality: the love of God and of Christ, which absolutely nothing must come before. And this his first and principal quality, Vincenzo Gioacchino Pecci learned here, in his native town, from his parents, from his parish.
But there is a second aspect, which derives from the primacy of God and of Christ and that one meets in the public action of every pastor of the Church, especially of every Supreme Pontiff, with the characteristics proper to each one. I would say that precisely the concept of “Christian wisdom,” which already emerged from the first reading and the Gospel, offers us the synthesis of this position of Leo XIII -- it is not by chance that it is also the “incipit” of one of his encyclicals. Every pastor is called to transmit to the People of God, not abstract truths, but a “wisdom,” that is, a message that joins faith and reason, truth and concrete reality. Pope Leo XIII, with the assistance of the Holy Spirit, was able to do this in one of the most difficult historical periods of the Church, remaining faithful to tradition and, at the same time, measuring it with the great open questions. And he succeeded in his efforts precisely on the basis of the “Christian wisdom,” founded on sacred Scriptures, on the immense theological and spiritual patrimony of the Catholic Church and also on the solid and limpid philosophy of St. Thomas Aquinas, which he appreciated in the highest way and promoted in the whole Church.
At this point, after having considered the foundation, that is, faith and the spiritual life, and therefore the general framework of the message of Leo XIII, I can turn to his social teaching, made famous and timeless in his encyclical “Rerum novarum,” but also richly expressed in multiple interventions that constitute an organic body, the first nucleus of the Church’s social doctrine. We take our cue from St. Paul’s Letter to Philemon, which happily the liturgy has us read precisely today. It is the shortest of all the Pauline epistles. During a period of imprisonment the Apostle transmitted the faith to Onesimus, a slave from Colossae, who had fled from his owner Philemon, a wealthy inhabitant of that city, who, along with his family, had become Christian through the preaching of Paul. Now the Apostle writes to Philemon, inviting him to welcome Onesimus no longer as a slave but as a brother in Christ. The new Christian brotherhood overcomes the separation between slaves and freemen, and it triggers in history a promotion of the person that will lead to the abolition of slavery, but also to the overcoming of the barriers that had existed up until then. Pope Leo XIII dedicated his 1890 encyclical “Catholicae Ecclesiae” precisely to the theme of slavery.
FULL SPEECHPapal Homily for Visit to Leo XIII's Birthplace (Zenit.org)