From Leo XIII to Leo XIV: 135 Years of Catholic Social Teaching

Leo XIII was a Catholic. Unfortunately, Leo XIV is turning out to be Francis 2.0, a modernist progressive wedded to the world and all that implies.

From Aleteia

By Daniel Esparza

In 1891 a pope spoke into the chaos of the Industrial Revolution. In 2026 his namesake spoke into the age of AI. The tradition connecting them is worth knowing.

On May 15, 1891, Pope Leo XIII published a letter addressed to the Catholic bishops of the world, but its subject was the condition of the working class in an industrializing Europe where factory workers labored in brutal conditions, owned nothing, and had no legal recourse. Rerum Novarum — “Of New Things” — defended the right to private property, called for just wages and humane working conditions, affirmed the right of workers to form unions, and insisted that neither unbridled capitalism nor revolutionary socialism offered an adequate account of the human person.

It was, in the most literal sense, a new thing. No pope had written like this before. And from it grew what is now known as Catholic social teaching — a body of doctrine that has been developing for 135 years, through wars and depressions and the rise and fall of ideologies, always returning to the same foundational claim: that the human person has an inviolable dignity, and that every social, economic, and political arrangement must be judged by whether it respects or violates that dignity.

The tradition, encyclical by encyclical

Forty years after Rerum Novarum, on the same date — May 15, 1931 — Pope Pius XI published Quadragesimo Anno, deepening his predecessor’s framework and introducing two principles that have remained central ever since: subsidiarity — the idea that decisions should be made at the most local level possible — and solidarity — the recognition that we are responsible for one another. Written between the two World Wars, with fascism and Stalinism rising across Europe, it warned against both the concentration of economic power in private hands and the totalitarian absorption of all social life by the state.

John XXIII contributed two major documents. Mater et Magistra (1961) expanded the tradition’s scope to address international development and the relationship between wealthy and poor nations. Pacem in Terris (1963) — written in the shadow of the Cuban Missile Crisis and addressed, for the first time, to “all people of good will” rather than only to Catholics — articulated a comprehensive account of human rights grounded in natural law. It remains one of the most important documents in the history of Catholic engagement with the modern world.

Paul VI brought the tradition into the postcolonial moment with Populorum Progressio (1967), arguing that authentic development cannot be reduced to economic growth — that it must be “integral,” encompassing the full flourishing of every dimension of the human person. His phrase “development is the new name for peace” entered the permanent vocabulary of Catholic social thought.

John Paul II gave the tradition three major texts. Laborem Exercens (1981) recovered the theological significance of human work as a participation in God’s creative activity. Sollicitudo Rei Socialis (1987) revisited Populorum Progressio and introduced a sharper critique of both liberal capitalism and communist collectivism. And Centesimus Annus (1991) — published on the centenary of Rerum Novarum, in the immediate aftermath of the fall of communism — offered a nuanced assessment of the market economy: affirming its capacity to produce wealth and freedom while insisting that it requires a strong moral and legal framework to prevent it from devouring the weak.

Benedict XVI’s Caritas in Veritate (2009) placed love at the center of the tradition, arguing that justice without charity is incomplete and that the global financial crisis revealed a deeper crisis of meaning and values. Francis brought Laudato Si' (2015) and Laudate Deum (2023), connecting ecological responsibility to social justice and insisting that the cry of the earth and the cry of the poor are the same cry.

And then came another Leo

On May 15, 2026 — the 135th anniversary of Rerum Novarum — Pope Leo XIV published Magnifica Humanitas. The date was not accidental. Leo XIV chose his papal name in honor of Leo XIII, and the choice of May 15 for his first encyclical placed him explicitly in the line of succession of the tradition his predecessor had begun. Where Leo XIII spoke into the industrial age, Leo XIV speaks into the age of artificial intelligence — asking what happens to human dignity when machines can perform allegedly “cognitive” labor, when algorithms make decisions about people’s lives, and when the concentration of technological power threatens to reproduce, in digital form, the same inequalities that Rerum Novarum confronted in the factories of the 19th century.

The thread running through all of it is single and consistent. Every document in this tradition, from 1891 to 2026, begins from the same place: the conviction that the human person is made in the image of God, that this gives every person an inviolable dignity that no economic system or political ideology can override, and that society’s institutions must be judged by whether they serve or undermine that dignity. The tradition is not a political program. It does not map onto the left-right spectrum, which is why both sides have claimed it and both sides have been disappointed. It is an anthropology — a set of claims about what the human person is — from which social conclusions follow. As the Catechism puts it: “The Church makes a moral judgment about economic and social matters when the fundamental rights of the person or the salvation of souls requires it.” That judgment has been making itself heard for a hundred and thirty-five years now.