In my home state, there has been vigorous debate about proposals to raise the state's minimum wage. This sort of proposal of course prompted fierce online debates between various factions, some arguing for, some against the proposed wage increase. It also brought out spirited debate among faithful Catholics on the concept of a just wage, and classical issues surrounding Catholic social teaching. The particulars of the minimum wage proposal are neither here nor there; I personally see very little correlation between contemporary economic discussions and the lofty ideals of Leo XIII and Pius XI. But what was very interesting in the discussions was the different approaches Catholics took to Catholic social teaching. Some were willing to grant it a sweeping authority, on par to the Church's dogmatic pronouncements; others were more dismissive. I recall in the minimum wage discussion one Catholic attorney, in responding to some citations of Leo XIII, remarked that "Rerum Novarum is hardly relevant in this discussion."
Now, one may be in favor of minimum wage increases or against them; we could certainly debate their merits. But how a Catholic could suggest that Rerum Novarum is "hardly relevant" to such discussions is beyond me. If Rerum Novarum is not relevant in a discussion about the minimum wage, where on earth is it relevant?
The fact is, for many Catholics the economic and social teachings of Leo XIII and Pius XI are matters of little concern or interest to them, if they are even known at all. In my experience, those Catholics who dismiss the work of these great pontiffs generally do so out of a preference for a kind of libertarian free market economy, usually influenced by Austrian economics. Having extolled the virtues of a completely unregulated economy, these Catholics are embarrassed by Leo XIII's condemnation of "the hardheartedness of employers and the greed of unchecked competition" and other such statements in Rerum Novarum, which to their ears sounds like socialist demagoguery. And to one immersed in the United States conservative sub-culture, with its exaltation of the cult of the individual and its transfiguration of wealth into a virtue, it is difficult to avoid such prejudices.
This is simply my experience; I admit it is a limited one, and that there are others who may disagree with me but for different reasons. Granted. Still, it is the purpose of this essay to examine this question of what authority Catholics are bound to give to Rerum Novarum and Quadragesimo Anno in particular, since these two encyclicals are the two columns upon which Catholic social teaching rests.
Thus, we will examine the text of these two encyclicals to see what authority Leo XIII and Pius XI grant to them. We will not be examining or commenting upon the content of these documents; this has been amply done elsewhere. Rather, we will restrict ourselves to the question of the authority of the text. In order to keep this study within reasonable bounds, we will also be restricting ourselves only to those statements in Rerum Novarum and Quadragesimo Anno. More could certainly be said, for example, if we were to look at statements by John Paul II or other more modern pontiffs on the importance of these encyclicals. Unfortunately, we shall have to restrain ourselves and save such a more expansive study for another time.
It is important to understand that we are not seeking to prove that these documents are infallible or contain infallible pronouncements; some have argued convincingly that the prerogative of infallibility applies to the pope's ordinary Magisterium as well (cf. John P. Joy, STL, Cathedra Veritatis: On the Extension of Papal Infallibility). But this is not our argument; we merely seek to prove that the these encyclicals are still authoritative and command the assent of the faithful, which is a different question from their infallibility.
One final word about the text: In both encyclicals we have used the official Vatican text distributed in English by the Daughters of St. Paul. This may deviate from the English found on the Vatican website. However, while using the text from the Daughters of St. Paul, we have retained usage of the numbering used on the Vatican website, which is very different than the numbering used in the Daughters of St. Paul editions. For example, Rerum Novarum 16 on the Vatican website is Rerum Novarum 24 in the Daughters of St. Paul. We chose the Vatican numbering because more readers will most likely reference these texts fromt he Vatican website rather than the printed Daughters of St. Paul edition. Thus we have retained the Daughters of St. Paul text while opting for the Vatican numbering.
I. Rerum Novarum
In the first place, let us consider the authority Pope Leo attributes to his teaching in Rerum Novarum.
"In this Encyclical, however, consciousness of Our Apostolic office admonishes Us to treat the entire question thoroughly, in that order that the principles may stand out in clear light, and the conflict may thereby be brought to an end as required by truth and equity" (Rerum Novarum, 2).
We note first off that the Pontiff is speaking by virtue of his Apostolic Office. This in itself is not surprising; since encyclicals are the organ of the pope's ordinary teaching Magisterium (cf. Humani Generis, 20), it follows that any encyclical is promulgated by virtue of the pope's Apostolic Office. This has a further implication, however: since encyclicals are the ordinary means by which the popes exercise their ordinary Magisterium, they demand consent .
This is even more true when the encyclical attempts to clarify or settle a contended point. In Humani Generis, Pope Pius XII noted with regard to papal teaching: "If the Supreme Pontiffs in their official documents purposely pass judgment on a matter up to that time under dispute, it is obvious that that matter, according to the mind and will of the Pontiffs, cannot be any longer considered a question open to discussion among theologians"  Now it is clear that Rerum Novarum is an official document promulgated by virtue of Leo XIII's Apostolic Office. Did Leo intend to pass judgment on a disputed matter in Rerum Novarum?
Indeed he did, for the purpose of promulgating the encyclical, according to the citation above, was "in that order that the principles may stand out in clear light, and the conflict may thereby be brought to an end" (RN, 2). Therefore, according to Pius XII, since Leo spoke authoritatively with an aim of settling conflict, the teachings of Rerum Novarum "cannot be any longer considered a question open to discussion."
Further evidence that the pontiff intended to use his Apostolic Office to settle a disputed point comes in chapter 16, where Leo XIII states:
"We approach the subject with confidence and surety by Our right, for the question under consideration is certainly one for which no satisfactory solution will be found unless religion and the Church have been called upon to aid. Moreover, since the safeguarding of religion and of all things within the jurisdiction of the Church is primarily Our stewardship, silence on Our part might be regarded as failure in Our duty" (Rerum Novarum, 16).
Again, it is made clear that the purpose of the encyclical is to settle a controversy (i.e., the "social question"), which necessitates the involvement of the Church. But more to the point is the second sentence, which states that "since the safeguarding of religion and of all things within the jurisdiction of the Church is primarily Our stewardship, silence on Our part might be regarded as a failure in Our duty." With this sentence, Pope Leo offers a justification as to why the Catholic Church is weighing in on the question of economics. Interestingly enough, he responds by saying that it is his duty to safeguard religion, and that to fail to speak out in this area would be dereliction of duty.
The implication, of course, is that economic policies and decisions do not exist in a vacuum. They have a moral dimension, and as such a direct relevancy to Catholic doctrine. Economic acts are moral acts, and like all moral acts they are fundamentally religious. This is why Leo states that addressing the economic problems of his day is essentially an exercise in the "safeguarding of religion." The Church therefore has not only a right but a duty to intervene; anything less would be construed as "failure in our duty."
Relating to our original question, this only strengthens the case for Rerum Novarum's authority. Roman Pontiffs have sometimes weighed in on questions which were not intrinsic to the Faith; but Leo here states that the principles he is addressing are so central to Faith that he considers the document an exercise of his prerogative to safeguard religion and part of his solemn duty as Successor of Peter.
Nor is the teaching of Rerum Novarum merely in the realm of exhortation, but rather of command. Leo XIII later speaks of the teachings of the encyclical as imperative:
"But the Church, with Jesus Christ as her teacher and leader, seeks greater things that this; namely, by commanding something more perfect, she aims at joining the two social classes to each other in closest neighborliness and friendship" (Rerum Novarum, 21).
Notice here that the language is not merely hortatory; it is imperative. Leo has already stated that he is intervening to settle a question that has implications for the Faith itself, and as such he sees this encyclical as a command or directive, much like any other act within the jurisdiction of the papacy.
"Furthermore [the Church] strives to enter into men's minds and to bend their wills so that they may suffer themselves to be ruled and governed by the discipline of the divine precepts. And in this field, which is of first and greatest importance because in it the whole substance and matter of benefits consists, the Church indeed has a power that is especially unique" (Rerum Novarum, 26).
It is difficult to see how Leo does not expect his teaching in Rerum Novarum to be assented to when he is saying that men must "bend their wills" and "suffer themselves to be ruled and governed." But more importantly, Leo states that the teaching he is promulgating is nothing other than "divine precepts." Again, economic questions are essentially moral, and as such fall within the pale of the Church's authority. Leo goes out of his way again to note that "in this field...the Church indeed has a power that is especially unique."
Leaving Rerum Novarum, we can say a few things with certainty: (1) Leo intended to speak by virtue of his Apostolic Office, that is, in his full authority as Supreme Pontiff (2) he intended to use his teaching as a means to settle disputed points (3) he asserts that these points pertain to the doctrine of the Christian religion and that hence he has a duty to intervene (4) that it is within the Church's competence to make authoritative declarations on matters pertaining to the "social question" and hence to economics and that (5) these declarations are not merely hortatory but are "commands" to which men must "bend their wills", and finally (6) that these commands are nothing other than "divine precepts."
Again, we are not seeking to prove that Rerum Novarum contains any infallible declarations per se, but rather that Leo XIII was speaking authoritatively with the intention of binding the entire Church to his teaching. Given the teaching of Pius XII on the authority of papal encyclicals and the language used by Leo XIII, it is hard to see how anyone could assert that Rerum Novarum is not authoritative or that Catholics may freely dissent from its principles, which Leo says are nothing other than "divine precepts."
II. Quadragesimo Anno
In 1931 Pope Pius XI promulgated Quadragesimo Anno in honor of the fortieth anniversary of Rerum Novarum. This document is perhaps even more fundamental to Catholic social teaching than Rerum Novarum, taking the principles of Leo XIII and fleshing them out to describe what an economy organized along the lines of Rerum Novarum would look like. However, as stated above, we are not here interested in the content of the encyclical but rather in its authority. Quadragesimo Anno is also helpful in this respect, for it makes several statements affirming the authority of Rerum Novarum, asserts its own authority forcefully, and clarifies questions about the level of assent which Catholics were expected to give these two documents.
In many cases, Pius XI simply echoes the words of Leo XIII while elaborating or offering his own commentary. For example, at the beginning of the encyclical, he reiterates Leo's earlier statement that the intervention of the Church was necessary in settling the "social question":
"Rerum Novarum, however, stood out in this, that it laid down for all mankind unerring rules for the right solution of the difficult problem of human solidarity, called the Social Question, at the very time when such guidance was most opportune and necessary" (Quadragesimo Anno, 2).
Note that the teachings of Rerum Novarum are said to be "unerring rules." We must not read too much into this word "unerring" (tutissimas, literally, "surest" or "most prudent"). Pius XI's use of this word does not render Leo XIII's statements inerrant in the sense of infallible; it is more along the lines of John Paul II's phrase "sure norm" when describing the doctrinal value of the Catechism of the Catholic Church.  It denotes that the teaching of Rerum Novarum is authoritative, just like John Paul's statement means the CCC is authoritative. Those who would deny Rerum Novarum is authoritative would be just as hard pressed to explain their case as those who deny the Catechism's authority.
A little later on, Pius XI repeats Leo's statement about the obligations of duty that prompted him to speak, but also adds that Leo's teaching in Rerum Novarum was decided "in virtue of the divine Magisterium committed to him":
"Long did the prudent Pontiff [Leo XIII] consider the matter before God, seeking the advice of the most experienced counselors available, and carefully weighing the reason for and against. At last, "urged by the responsibility of the Apostolic Office", and lest by keeping silence he should seem to neglect his duty, he decided in virtue of the divine Magisterium committed to him, to address himself to the Universal Church of Christ, nay, to the whole human race" (Quadragesimo Anno, 8).
Again, this repeats Leo's words but also deepens them by citing the teachings of Rerum Novarum as part of the "divine Magisterium", again reaffirming the authoritative nature of this encyclical.
Since 1891, Catholic social teaching had been greeted with mixed reactions from the Catholic world. Those who were more attached to either Communist or Capitalist economic theories tended to argue that the Roman pontiff had no right to interfere in economic matters; that such questions were outside the realm of the papal Magisterium's authority. Pius XI's words above certainly dispel this notion, but in Quadragesimo Anno 11 we see a fuller justification of the pope's right to pass judgment on economic matters. Here Pius XI states:
"The Sovereign Pontiff approached the subject in the exercise of his manifest rights, deeply conscious that he was the chief guardian of religion and the chief dispenser of all that closely appertains to it; for the question at issue was one to which "no solution could be found apart from the intervention of religion and the Church." Basing his doctrine solely upon the unchangeable principles drawn from right reason and divine revelation, he indicated and proclaimed with confidence and "as one having power", "the relative rights and mutual duties of the rich and the poor, of Capital and Labor..." (Quadragesimo Anno, 11).
This passage merits close attention. First, as Leo invoked his duty as guardian of the Christian religion, Pius says that the papal teaching of Rerum Novarum was "in the exercise of his [Leo's] manifest rights", again, because of the fundamental moral aspect of economic decisions. But Pius will go on to clarify exactly in what sense the teachings of Catholic social teaching are part of the Christian religion: speaking of Pope Leo, he says that he was "deeply conscious that he was the chief guardian of religion, and the chief dispenser of all that closely appertains to it." This last phrase is essential, as it seems to identify Catholic social teaching, not as divine revelation, but as something that "closely appertains to it." Traditionally, this would be a truth which is called sententia ad fidem pertinens. These truths (also called sententia certa) are those which have not been infallibly defined but whose truth is guaranteed by its intrinsic connection with the doctrine of revelation .
This is what Pius XI means when he refers to the truth of the Catholic religion "and of all that closely appertains to it." The only question is whether that last phrase is meant specifically to refer to Leo's teachings in Rerum Novarum; the context of the passage leaves room for argument, but given that one of Pius XI's ends in publishing Quadragesimo Anno was to clarify the authority of Rerum Novarum, it seems unlikely he would mention truths closely pertaining to revelation if he did not intend to assign this level of theological certainty to the subject at hand.
The latter part of the above-cited passage is also important. "Basing his doctrine solely upon the unchangeable principles drawn from right reason and divine revelation, he indicated and proclaimed with confidence and "as one having power", "the relative rights and mutual duties of the rich and the poor, of Capital and Labor..." Again, Pius XI is intending to affirm that the economic principles affirmed in Rerum Novarum are not the product of some merely human theories, but are deduced "from right reason and divine revelation", and hence are binding and authoritative on the faithful, which is why Leo is said to have proclaimed them "as one having power." The Catholic who would suggest that the teaching of Rerum Novarum is not binding would have to explain why they were free to dissent from a teaching deduced "from right reason and divine revelation" and promulgated by the pope "with confidence and as one having power." Clearly, neither Pope Leo XIII nor Pius XI would have entertained the idea that Rerum Novarum is not binding or that Catholics are free to proffer opinions opposed to its teachings.
We shall see a little later on that Pius XI underscores the economic doctrines of Leo XIII and of Quadragesimo Anno with nothing less than the full authority of Jesus Christ Himself. Let us jump forward to Chapter 15:
"The Church insists, on the authority of the Gospel, upon those teachings whereby the conflict can be brought to an end, or rendered at least far less bitter. The Church uses her efforts not only to enlighten the mind, but to direct by her precepts the life and conduct of each and all" (Quadragesimo Anno, 17).
Here Pius XI is no longer simply reminiscing on the teaching of Rerum Novarum, but is speaking about the principles he himself is elaborating upon in Quadragesimo Anno. These principles of moral and economic life are said to rest not upon some man-made economic theory, but "on the authority of the Gospel." Those who think little of dissenting from these documents need to pause and ponder this comment; the teachings of Rerum Novarum and Quadragesimo Anno are said to rest "on the authority of the Gospel." In other words, the principles of Catholic social teaching are the principles of the Gospel. Since the Magisterium is not above the Gospel but is its servant , a teaching promulgated "on the authority of the Gospel" is given with the very highest authority.
Similar to this, we see the teachings of Rerum Novarum are later referred to simply as "the Catholic truths". Pius XI states:
"Thus, too, We rejoice that the Catholic truths, proclaimed so vigorously by our Predecessor, are advanced and advocated not merely in non-Catholic books and journals, but frequently also in legislative assemblies and courts of justice" (Quadragesimo Anno, 21).
This usage of the phrase "Catholic truths" to describe the teaching of Rerum Novarum is interesting. "Catholic truths" are those truths which must be believed with divine and Catholic faith. This terminology is in reference to the dogmatic definition of Vatican I, which stated that "All those things are to be believed by divine and Catholic faith which are contained in the written Word of God or in Tradition, and which are proposed by the Church, either in solemn judgment or in its ordinary and universal teaching office, as divinely revealed truths which must be believed." Pope Leo himself would repeat Vatican I's terminology in his 1896 encyclical Satis Cognitum on the unity of the Church. Thus, by referring to the teaching of Rerum Novarum as "Catholic truths", Pius XI is situating Leo's teaching as truths to be believed with divine and Catholic faith; in other words, "as divinely revealed truths which must be believed."
Pius goes on to declare Leo's teaching to be taken as authoritative:
"Worthy of all praise, therefore, are the directions authoritatively promulgated by Leo XIII, which served to break down this opposition and dispel these suspicions" (Quadragesimo Anno, 31).
And, as if to remove all doubt concerning the pivotal place of Rerum Novarum in the Church's social doctrine, Pius XI makes this astonishing statement:
"Leo's Encyclical has proved itself the Magna Carta on which all Christian activities in social matters are ultimately based" (Quadragesimo Anno, 39).
The Magna Carta, of course, is taken by English jurists to be the foundation of the whole shambling edifice of British law. The call Rerum Novarum the Magna Carta "on which all Christian activities in social matters are ultimately based" is to grant it a tremendous authority, establishing it as foundational and central. One wonders, in what sense can Leo XIII's teaching be "the Magna Carta on which all Christian activities in social matters are ultimately based" if one does not regard it as authoritative? Pius goes on to address those who dissent from Leo XIII's teaching or who try to dissimulate by saying that the economic and social teachings of Rerum Novarum are not binding on Catholics:
"Nevertheless, there are some who seem to attach little importance to this Encyclical and to the present celebration...In the course of these years, however, doubts have arisen concerning the correct interpretation of certain passages of the Encyclical or their inferences, and these doubts have led to controversies, even among Catholics, not always of a peaceful character. On the other hand, the new needs of our age and the changed conditions of society, have rendered necessary a more precise application and amplification of Leo's doctrine. We, therefore, gladly seize this opportunity of answering these doubts, so far as in Us lies, and of satisfying the demands of the present day. This We do in virtue of Our Apostolic office by which We are a debtor to all" (Quadragesimo Anno, 40).
Notice the language here. Two classes of people are identified. Those who "attach little importance to this Encyclical" (i.e., Rerum Novarum), and those who have expressed "doubts" about the correct understanding of the Church's social teaching. When Pius states that he will "gladly seize this opportunity of answering these doubts", he is meaning to counter both classes - to those who dispute the meaning of Rerum Novarum, he will elaborate its principles authoritatively; and to those who deny that Rerum Novarum is authoritative and central to the Church's social mission, he will demonstrate its absolute centrality and authority.
In many cases, those who attach little importance to the Church's social teaching on economic matters will make the case that the Church "has no economic system" and that the Church is not competent to make pronouncements on economic matters. The Church, they say, can only give broad, moral principles, which Catholics must then apply to economics. But economics itself is beyond the pale of the Church's realm of authority and competence, inasmuch as it does not deal with faith or morals. Just as chemistry or mathematics cannot come under the realm of Church authority, so also is economics autonomous.
Of course, these persons who are overzealous to make economics a science forget that, while there are scientific aspects to economics, economics is one of the social sciences because it deals fundamentally with the actions and motivations of men. Physics, mathematics, etc. are hard sciences, which means they have a greater objectivity, methodological rigor, and degree of exactitude. The object of the hard sciences are the quantifiable aspects of the world; the object of the social sciences is man himself, with his motivations, actions, judgments, etc. Because of this, economics, as a social science, is fundamentally concerned with the moral actions of men and as such falls within the competence of the Magisterium to make pronouncements on. Pius XI states this quite unambiguously:
"We lay down principles long since clearly established by Leo XIII, that it is Our right and Our duty to deal authoritatively with social and economic problems" (Quadragesimo Anno, 40).
Many would accept the Church can deal with social problems, but deny the Church any prerogative in economic matters. Pius's pronouncement puts that objection to rest by categorizing problems "economic" as distinct from problems "social" and affirming the Church's "right and duty to deal authoritatively" with both. Again, economic matters fall under the moral law, and as such are part of the "deposit of truth entrusted to us by God":
"For the deposit of truth entrusted to us by God, and Our weighty office of propagating, interpreting and urging in season and out of season the entire moral law, demand that both social and economic questions be brought within Our supreme jurisdiction, in so far as they refer to moral issues" (Quadragesimo Anno, 40).
Hence, the duties of the pontificate "demand that both social and economic questions be brought within our supreme jurisdiction." Now, many will note Pius's qualifier, "in so far as the refer to moral issues" and move from that to exempting almost the entire science of economics from the Church's jurisdiction. Now, it is true that economics has non-moral elements; it encompasses aspects of mathematics, logistics, demographics, and more. But these are not economics proper; these are rather the handmaids or tools of the economist. Economics proper (to use the classic textbook definition) is the study of how choices are made to allocate limited resources to satisfy unlimited needs. The Church does not get bogged down in the mathematics of economics, but it does insist that the substance of economics - the moral decisions made by men - conform to Gospel principles.
The Magisterium has made fairly sweeping pronouncements of what it considers to be subject to Gospel principles: wages, unions and union negotiations, the sort of work that can be demanded of the worker, who is fit to do what sorts of work, what constitutes a reasonable work week, time off, the ends and means of labor, relationship between capital and labor, what is a just profit, relationship between governments and capital, amount of proper government regulation, principles of taxation, agricultural economy, morality in the workplace, definitions of the living wage, obligations care for the poor, advantages and disadvantages of state welfare programs, savings, land ownership, and principles of mediation and arbitration by subsidiary bodies. All of these subjects are placed under the authority of the Church by Rerum Novarum and Quadragesimo Anno. The economist may throw up his hands and say, "That's practically the entire discipline of economics!" Exactly.
And what Leo taught on was not simply a matter of opinion, but was nothing other than Catholic doctrine:
"...[S]ince controversy has arisen among Catholics as to the true sense of Pope Leo's teaching, We have thought it well to defend from calumny the Leonine doctrine in this matter, which is also the Catholic doctrine, and defend it against false interpretations" (Quadragesimo Anno, 44).
Well and good. But perhaps this teaching is no longer applicable? The Church, in her pastoral concern for the situation of men, frequently makes pronouncements that are particularly oriented towards the needs of a specific age. For example, many, including Cardinal Ratzinger, have noted that the language of Gaudium et Spes represents the particular context of the world of the 1960's and is characterized by an optimism about modernity that the 21st century finds embarrassingly inadequate. We can find many similar pronouncements from the Reformation or medieval eras that are particularly suited to those times and places and which are of little force today because the socio-political conditions they were meant to address no longer exist.
Perhaps a similar argument can be put forward for Rerum Novarum? The industrial capitalism and rampant poverty of the 1890s is a far cry from the diversified "service sector" capitalism we have today. Perhaps, given the great affluence of the capitalist west in the post-World War II era, the teachings of Leo XIII and Rerum Novarum look increasingly like principles suited to the late 19th century but of little force or value today? Pius XI rules out such an easy dismissal of Leo's great work:
"...[T]hese salutary injunctions of the Pontiff [Leo XIII] have not infrequently been forgotten, deliberately ignored, or deemed impractical, though they were both feasible and imperative. They have lost none of their force or wisdom for our own age, even though the horrible "pauperism" of the days of Leo XIII is less prevalent today" (Quadragesimo Anno, 59).
As of 1931, the teachings of Leo had "lost none of their force of wisdom for our own age." This is common sense; we have seen that Leo and Pius go out of their way to identify the teachings of Rerum Novarum with the Gospel itself. Just as the Gospel never loses its force, so Rerum Novarum retains its authority. This is even more so in light of the constant reaffirmations of Leo's encyclical which have come from Paul VI, John Paul II, and Benedict XVI.
Much further on in Quadragesimo Anno, Pius XI makes an interesting statement:
"What will it profit to teach them sound principles in economics , if they permit themselves to be so swept away by selfishness, by unbridled and sordid greed, that "hearing the Commandments of the Lord, they do all things contrary"? (Quadragesimo Anno, 131)
Again, to those who suggest that Catholic social teaching merely addresses moral questions without touching on economics, Pius responds that the Church's teaching truly does put forward "sound principles in economics", which obviously he could not say unless it was asserted that the Church had the right, duty and competence to teach "sounds principles in economics." It is also interesting that he contrasts "sound principles in economics" with "selfishness" and "unbridled and sordid greed", the characteristic traits of unrestrained capitalist competition (cf. "On Objective and Subjective Ends of Work", USC). The only remedy for this capitalistic "unbridled and sordid greed" is a return to sound Catholic economic principles:
"For this pitiable ruin of souls, which if it continue, will frustrate all efforts to reform society, there can be no other remedy than a frank and sincere return to the teaching of the Gospel" (Quadragesimo Anno, 136).
We have seen numerous times how Catholic social teaching is identified as "the Catholic faith", "Catholic truth" and the principles of the Gospel. Here again it is simply called "the teaching of the Gospel", which grants it tremendous authority. And Pius does not simply present the Catholic economic principles of Leo XIII and his own Magisterium as one interesting option among many, but suggests that the very survival of society depends upon adherence to them, and even that their refusal will entail the "pitiable ruin of souls." This could simply mean that failure to address the modern economic problems will lead to more atheism and more Communism (as Pius XI would teach six years later in Divini Redemptoris), but it could also be taken to mean that, because of the great authority the popes assign to these teachings, dismissal or rejection of them constitutes a sin against faith and hence endangers ones eternal salvation.
Pius ends his encyclical by praising both clergy and laity who have undertaken to defend the Church's social teaching and once again to reaffirm the Church's right to address the contemporary socio-economic problems:
"We rejoice to see [clergy and laity] daily taking part in this great work and affording valuable help, [as well as] Our beloved sons devoted to Catholic Action, who with extraordinary zeal aid Us in the solution of social problems, in so far as the Church in virtue of her divine institution has the right and duty to concern herself with them" (Quadragesimo Anno, 138).
As an aside, this is a good passage to point to when enemies of Tradition suggest the pre-Conciliar Church kept the laity out of any meaningful apostolate; here we see Pius commending and encouraging the work of lay workers in promoting Catholic social teaching. But more important to our discussion, we see an affirmation of the Church's "right and duty" to concern herself with social and economic problems, which she does "in virtue of her divine institution" - and anything she does in virtue of her divine institution is nothing to be taken lightly.
Our original question was to sort out the question of what authority a contemporary Catholic is bound to give to the social teachings of Leo XIII and Pius XI. While there is much more that could be said, a few conclusions seems obvious:
First, Leo XIII and Pius XI certainly intended their teachings to be promulgated authoritatively and for them to be accepted with docility by the Catholic faithful. Their constant language when referencing their own teachings makes this conclusion unavoidable.
Second, given that encyclicals are the normative means of the exercise of the ordinary papal Magisterium, and that Pius XII taught that "if the Supreme Pontiffs in their official documents purposely pass judgment on a matter up to that time under dispute, it is obvious that that matter, according to the mind and will of the Pontiffs, cannot be any longer considered a question open to discussion among theologians" , and that greater weight is given to such ordinary teachings when they are repeated by many consecutive popes, it seems obvious that Catholic social teaching - including its economic statements - is part of the ordinary papal Magisterium and must be granted assent of the faithful, at least in those aspects which have been repeated and reaffirmed over time. 
Third, the reaffirmations of these two encyclicals by subsequent popes (for example, Centesimus Annus of John Paul II) in addition to the clear teaching of Pius XI that Leo XIII's teachings retain their validity make it undeniable that these encyclicals maintain a permanent authority. This follows from the identification of their teaching with "the Catholic faith" and "the principles of the Gospel."
There is much more that can be said. As mentioned above, this is not to suggest that these encyclicals contain infallible statements or that there may not be particular aspects of them which are less authoritative than others. But it does mean that the interlocutors's comment we opened with, that "Rerum Novarum is hardly relevant" in contemporary economic discussions, is manifestly false.
 Pius XII stated that Encyclicals must be given assent, even if they are not making infallible declarations: "Nor must it be thought that what is expounded in Encyclical Letters does not of itself demand consent, since in writing such Letters the Popes do not exercise the supreme power of their Teaching Authority" (Humani Generis, 20).
 St. John Paul II, Fidei Depositum, 3 (1992)
 The definition given by Dr. Ludwig Ott in Fundamentals of Catholic Dogma, "The Theological Grades of Certainty", § 4
 CCC 86
 First Vatican Council, Dogmatic Constitution on the Catholic Faith III, 8
 Humani Generis, 20
 There are many Catholic social teaching documents and many of them make statements which have in fact not been reaffirmed or stressed in subsequent documents. While all the teachings of Rerum Novarum and Quadragesimo Anno have been reaffirmed many times, the same cannot be said, for example, of Benedict XVI's acceptance of globalism as a fait accompli in Caritas in Veritate, something which is entirely absent from Rerum Novarum and Quadragesimo Anno. Statements found in Catholic social teaching have tended to become more sprawling and unrestrained in the post-Conciliar period, which is why we have restricted ourselves to the two great encyclicals of the pre-Conciliar period.