Leo XIII’s engagement with the concern of workers was a definitive shift in the Church’s response to social and political upheaval. His immediate predecessor, the arch-reactionary and antisemite Pius IX (r. 1846–1878), saw calls for social change primarily as a threat to the political and financial privileges of the Church — above all, to the pope’s sovereign rule over the Papal States, which he believed was unquestionable and ordained by God.

That belief was not shared by many of his subjects. In 1849, revolutionary forces temporarily deposed him during the short-lived Roman Republic, and in 1870, Italian forces captured Rome and permanently integrated the Papal States into the secular Kingdom of Italy. Pius IX responded with theological firepower, issuing encyclicals that railed against “communism” and “socialism” — terms that had gained new political resonance after the 1848 revolutions and the publication of the Communist Manifesto that same year. Yet his condemnations, typified by Nostis et nobiscum (1849), showed little awareness of the social and economic changes driving this new political radicalism. For Pius, Europe’s political turmoil was simply the work of “crafty enemies of the Church and human society” stirring up the masses, “whom they have deceived by their lies and deluded by the promise of a happier condition,” luring them to rob their social superiors and despoil the Church’s wealth. He even intimated that the communists might be conspiring with the Protestants to achieve this end. Whatever one makes of the theological and political content of these denunciations — and many Catholic thinkers have since challenged them — Pius IX offered little substantive economic analysis beyond to the insistence that workers and the poor should know their place.

It was in this context that Leo XIII assumed the papacy in 1878. In some respects, he continued Pius IX’s reactionary stances. Leo never acknowledged the legitimacy of Italian rule in Rome, even if the liquidation of the papacy’s military capabilities meant he was powerless to reclaim the territories Pius had lost. In his 1885 encyclical Immortale Dei, Leo joined in his predecessor’s condemnation of the ideas of popular sovereignty and press freedom. Even Rerum novarum, while rightly seen as a landmark document on labor issues, begins by expressing concern about political revolution.

As is customary, the encyclical is known by its “incipit,” its opening words — Rerum novarum — sometimes translated literally as “of new things” to emphasize Leo XIII’s willingness to address social and economic change. But this rendering is misleading: rerum novarum is a Latin idiom referring to political revolutions. Leo XIII justifies his turn to economic topics by explaining that the “lust for revolution that has been stirred up” (rerum novarum semel excitata cupidine) will naturally lead to demands for economic changes as well — exactly the reverse of the Marxist contention that political shifts follow from economic causes.

What distinguishes Leo XIII’s approach from his reactionary predecessor — and what makes the publication of Rerum novarum a watershed moment in the history of the Church — is that Leo does not stop at moralizing denunciation of this “lust for revolution.” Though far from a revolutionary, Leo understood that in a secularizing world, the Church could no longer argue from authority alone. Much of his papacy was dedicated to the revitalization of scholarship and philosophy within the Church, with the aim of making a more persuasive case for Catholicism to people who could no longer be compelled to obey.

Similarly, in Rerum novarum, Leo recognized that a credible Catholic response to the industrial revolution had to begin with an analysis of the economic forces at play. Leo XIII depicts a world where “workingmen have been surrendered, isolated and helpless, to the hardheartedness of employers,” and where “a small number of very rich men have been able to lay upon the teeming masses of the laboring poor a yoke little better than that of slavery itself.” He repeats Pius IX’s condemnations of socialism, and laments that socialists can exploit these conditions to spread their heretical message. But in doing so, Leo admits that inequality and economic oppression are real problems the Church cannot afford to ignore. While he rejects socialist solutions, Leo’s criticisms rest not on the absolutism of papal authority or on the invocation of divine revelation but on secular arguments about political economy.

By discussing these things in a papal encyclical, an official and authoritative statement of doctrine, Rerum novarum established a clear precedent that economic questions were within the scope of Catholic moral reflection — thus inaugurating a tradition of Catholic social teaching. The significance of Rerum novarum can be seen from the very titles of subsequent popes’ encyclicals on social issues: Pius XI’s Quadragesimo anno (“In the fortieth year,” 1931) and John Paul II’s Centesimus annus (“The hundredth year,” 1991) both define the 1891 publication of Rerum novarum as a critical milestone in Catholic engagement with the modern world. Pius XI described it as “the Magna Carta upon which all Christian activity in the social field ought to be based,” and subsequent popes and Catholic writers of all kinds have cited it extensively.

While Rerum novarum undeniably shaped generations of Catholic social reformers and thinkers, the analysis and proposed solutions it offers are somewhat confused and disappointing. Although Catholic critics of capitalism are likely to invoke Rerum novarum, those who cite it in detail are more likely to be free-market conservatives. That’s because the heart of Rerum novarum’s political theory — and the basic premise underlying its prescriptions — is the idea that class conflict is an illusion, and not something that arises inevitably in a market economy based on private enterprise.

“The great mistake made in regard to the matter now under consideration,” says Leo XIII,

is to take up with the notion that class is naturally hostile to class. . . . Just as the symmetry of the human frame is the result of the suitable arrangement of the different parts of the body, so in a State is it ordained by nature that these two classes should dwell in harmony and agreement, so as to maintain the balance of the body politic. Each needs the other: capital cannot do without labor, nor labor without capital.

This vision of capitalism as a harmonious and organic unity of cooperating classes is unlikely to persuade a Marxist — or any other socialist — or indeed anyone with firsthand experience of life in a capitalist society. And the description of class society as “ordained by nature” will be equally unpersuasive to those familiar with the historical details of how capitalism emerged and supplanted other modes of production.

Leo XIII did recognize that this harmony between capital and labor was not to be found in Europe, and he had a ready explanation: the declining influence of the Catholic Church. For Leo, the problem of class conflict had arisen from insufficient faith, and the solution lay in religion’s unifying power. “The Church, with Jesus Christ as her master and guide,” he wrote, “tries to bind class to class in friendliness and good feeling.” Lacking any material or structural account of the causes of class conflict — and unwilling to entertain the proposals of the socialists — Leo put his faith in a supernatural solution.

This is not to say that Leo was completely without practical recommendations. The pope praised labor unions as a means for workers to defend their interests, though he believed they should be organized along sectarian lines, to shield Catholic workers from “heretical” ideas. He supported regulation of working hours, conditions, and child labor. And, acknowledging the painful problems caused by an unequal distribution of wealth, he argued in vague terms that “the law, therefore, should favor ownership, and its policy should be to induce as many as possible of the people to become owners.”

From a nineteenth-century perspective, Leo XIII’s proposals may have seemed progressive enough. But in proposing remedies for the sufferings of capitalist society, Leo XIII was constrained by a belief in the sanctity of private property that ruled out any redistributive solutions. The first part of Rerum novarum is devoted to defending a natural right to own private property, echoing arguments made by John Locke and other early liberal thinkers. Though he criticizes the rich for using their wealth to dominate and oppress the working class, he insists that “this great labor question cannot be solved save by assuming as a principle that private ownership must be held sacred and inviolable.” He urged the rich to use their wealth for the common good — but emphasized that doing so was a matter of “Christian charity — a duty not enforced by human law.”

Curiously, Rerum novarum makes no reference at all to the traditional treatments of property in canon law and by Catholic philosophers like Thomas Aquinas, who argued that private property is a product of human agreement, not natural law — and that the needy have a moral right to the excess goods of the rich. Bypassing this tradition, Leo denounced socialism as an affront to reason as well as faith and warned that efforts toward redistribution of wealth were doomed to failure — for “all striving against nature is in vain.”

Taken at face value, these elements of Rerum novarum appear to reject the core of progressive politics. And in his fear of socialist revolution, that may well have been what Leo XIII intended: a modest, paternalist program that would alleviate some of the suffering of workers while preserving the capitalist order. Then as now, there were Catholics eager to invoke the authority of the Catholic Church against any movement for social change. But if the text of Rerum novarum can be discouraging on this front, its legacy has taken a different path — one that may offer insight into what Leo XIV now hopes to revive or reinterpret.

Given the exalted status of the papacy among Catholics, overt rejection of a papal encyclical — whether by successor popes or by other Catholic thinkers — is extremely rare. Still, later contributions to Catholic social teaching, even when couched in praise for Leo XIII and his writings, have tended to moderate his conclusions in ways that open a door to a fuller critique of capitalism and less tentative solutions.

In 1931, Pius XI, while effusively praising Leo’s wise judgment, set aside the idea that private property should be “sacred and inviolable” and suggested carefully that the state might “determine more accurately upon consideration of the true requirements of the common good what is permitted and what is not permitted to owners in the use of their property.” And in 1967, Paul VI, while insisting that he was following in Leo’s footsteps, argued that the common good sometimes requires the expropriation of private property. In 2015, Pope Francis went so far as to insist that “the Christian tradition has never recognized the right to private property as absolute and inviolable, and has stressed the social purpose of all forms of private property.”

On the subject of class conflict, the popes have followed a similar trajectory, and the vision of harmoniously collaborating classes has been replaced with reminders that social struggle should proceed without hatred or narrowly partisan interest.

Despite the tendency of subsequent popes to modify or quietly ignore the specific content of Rerum novarum, the encyclical’s prestige as the founding document of Catholic social thought has endured. And if the newly elected Leo XIV has positioned himself as continuing the work begun by Leo XIII, it is almost certainly this broader tradition — and not the letter of Rerum novarum — that he has in mind. In an address to a conference on Catholic social teaching at the Vatican on May 17 — less than ten days into his papacy — the new pope made some comments that hint at how his interpretation of this tradition might unfold.

The Catholic Church, Pope Leo says, “does not claim to possess a monopoly on truth” — a provocative remark, and one at odds with the positions of some of his predecessors, who tended to distrust and fear any social movements or economic theories that developed outside of the Church’s maternal guidance. Even as he sat on a throne in the Clementine Hall of the Apostolic Palace, Leo described the Church’s “social doctrine” not as a pronouncement handed down from on high but as a process of learning and engagement: “Doctrine is not the same as an opinion, but is rather a common, collective, and even multidisciplinary pursuit of truth.” For Leo XIV, this pursuit must be based on “a commitment to encounter and listen to the poor.”

Leo’s call for dialogue and encounter is far removed from his namesake’s magisterial pronouncements about the sanctity of private property. Needless to say, it isn’t an official endorsement of left-wing politics. Nevertheless, the new pope’s framing seems to suggest a continuation of the intellectual openness and readiness to consider perspectives from outside the Catholic Church which were a controversial hallmark of Pope Francis’s reign. For advocates of progressive economic policy who hope to engage with Catholics, this may be an encouraging sign. In Leo XIII’s time, the Church’s enthusiastic defense of private property and a market economy reflected fears that anti-capitalist agitation posed an existential threat to both the Church’s institutions and its moral authority. Such reactionary fears have not totally disappeared from Catholicism, but more than a century of historical experience and engagement with social movements has gradually reshaped the Church’s perspective. 

Leo XIV does not seem to be concerned whether private capital will be available as a political bulwark for the Church. Instead, his comments suggest a fear that an increasingly inhuman, algorithmically driven, and unregulated economy will endanger the basic values of “human dignity, justice, and labor.” The liberal economic principles of Rerum novarum are unlikely to provide a satisfying solution here. But Catholic social teaching is more than a single document, and Leo XIV can draw on the resources of a tradition that has meditated for centuries on the dangers of greed, the sin of seeking domination over others, and the primacy of the common good.

The unexpected election of a US citizen to the papal throne has naturally been a source of pride for many in his country of origin, even if his track record of rebuking US politicians (including the recent Catholic convert J. D. Vance) gives some conservatives pause. In the United States, where right-wing donors and influencers tend to shape perceptions of the Catholic Church, the tradition of Catholic social teaching descended from Rerum novarum is often expounded in a way that favors free markets, “small government,” and inviolable property rights. Leo XIV’s invocation of the encyclical may be interpreted in that light by some. But he is not only a US citizen. In 2015, he acquired citizenship in Peru, where he had spent most of his career and was serving as Bishop of Chiclayo.

In Peru — the birthplace of liberation theology — to invoke “Catholic social teaching” does not imply reflexive anti-communism. If often reflects a critique of market economies’ failure to serve the poor and a call for redistribution of property and robust welfare systems. Time will tell whether the first US-born pope owes more to his North American or South American influences.