When the encyclical Humanae vitae was promulgated in 1968, its teachings were widely contested—and notably belated. The question of birth control was supposed to have been decided at the Second Vatican Council (1962–65), for inclusion in Gaudium et spes. But differences among the council fathers were so profound that agreement proved impossible, so a commission of clerical and lay experts was formed to study the question and help the Holy Father prepare a postconciliar encyclical.

Though the discussions of this commission were kept under strict secrecy, many prominent Catholic intellectuals, both laymen and clergy, were keenly interested in its workings. One such layman was Jacques Maritain, the philosopher and convert to Catholicism who, at the close of Vatican II, had received from Pope Paul VI the council’s message to the intellectuals of the world; and one such cleric was Cardinal Charles Journet, theologian of the papal household and adviser to Paul VI. Maritain and Journet were longtime friends—the former had chosen the latter as his “confidant-théologien” years before—and from their first meeting in 1920 until Maritain’s death in 1973, they exchanged 1,774 letters. Publication of this prodigious correspondence was completed in 2008 with the appearance of a sixth and final volume.

As readers of these letters will discover, decades before Humanae vitae Maritain and Journet were already taking up the church’s position on contraception, especially in response to the 1930 encyclical Casti connubii and its interdiction of all forms of birth control other than the “natural” rhythm method. In the face of pressure from Roman authorities and local ecclesiastical superiors—there was discussion in the curia of placing some of Maritain’s books on the Index, and Journet risked being relieved of his position as professor of theology at the seminary in Fribourg—neither man dared to go public with his reservations, and after the 1940s there followed a long silence on the subject.

Then Maritain, during his 1958 stay at Princeton University, once again broached it. Discussing the recently invented birth control pill, he invoked a distinction between the finis operis (the intrinsic end or purpose of an act) and the finis operantis (the end or purpose of the actor). In the former case, Maritain felt it was easy to distinguish between what is natural and what is against nature (sexual intercourse was teleologically ordered to procreation), while in the latter, a distinction between the use of the rhythm method and the use of the pill struck him as “vain and futile.” “I have met young Catholic professors who already have seven or eight children and for whom the problem of additional births would be tragic,” he wrote to Journet. “Has the church made a pronouncement on the subject of these pills? Would their use be licit while waiting for the church to make such a pronouncement?” In reply, Journet sent a copy of a papal document forbidding the use of pills for the limitation of births, and remarked: “I too would hope that their use be permitted: I find your distinction well founded. Alas I see the opinion of the moralists running in the opposite direction.” He went on to speculate whether using the pill to “regularize” ovulation and thus maximize the effectiveness of the rhythm method might be “legitimate and in conformity with nature.”

The back-and-forth between the two men picked up again after the council, when both speculated on the secret proceedings of the Birth Control Commission and on such information as might have leaked. Having learned that the committee of theologians had voiced a majority for authorization of use of the pill on the principle that the intervention of right reason in natural things is evidently legitimate, Maritain related to Journet his view “that the theologians against regulation and those in favor of it both invoke principles that are too broad, and do not take enough account of the means employed.” “In my opinion,” he went on, “there is no essential difference between the pill and the other methods, between a mental calculation and a medical intervention.” Maritain concluded by asserting that while “the moral condemnation brought against any means that violate the opus should be held as immutable...the situation has changed with the discovery of these other means, and their moral condemnation cannot be justified by reason.”

In his reply Journet suggested that Maritain “may have found a path to the solution of this problem.” Citing Pius XII’s 1951 “Allocution to Midwives,” which condemned any attempt by spouses to interfere in the accomplishment of the conjugal act or its natural consequences in order to prevent procreation, he asked—with evident frustration—“Can’t we get beyond this?” Maritain wrote back: “By means that violate the opus itself I understand the means used in the very accomplishment of the act. Aren’t these the means that were in use at the time when Pius XII delivered his allocution [that is, before the pill]? And can’t his text be understood as having in view those particular means?” Two letters later, Journet remarked that “according to certain moralists, the pill is considered even more pernicious than other contraceptives because it attacks not a transitory act, but a state.”

Both Maritain and Journet were close friends of the pope. As French ambassador to the Vatican (1945–48), Maritain had worked closely with the future Paul VI when (as Cardinal Montini) he served as papal secretary of state, while Journet had participated in the council as a theologian and adviser to Paul VI. Both were sympathetic to the situation of a pope caught between conflicting sides on the question of birth control. Writing to Journet, Maritain scoffed at cardinals, bishops, and experts who were zealous to defend their own authority “more than anything else (more even than the defense of the faith),” and expressed sympathy for the pope and “the impossible situation in which he finds himself.” Raising the distinction he had made before, Maritain asserted that “the progress of science has changed things, and—now permitting the use of means which satisfy the finis operantis without violating the end of the opus—brings it about that the use of these means, if they are used according to right reason, is not, in itself, morally evil.” The church, he concluded, “could authorize these means without contradicting itself.” In other words, there was no moral difference between employing the rhythm method and using the pill. Maritain considered writing something to this effect for Journet to give to the pope, but declared himself “horrified at the thought of butting into something that is not my business,” and asked his friend: “Tell me, Charles, if I am right to believe that I should not involve myself in all this, and that...the pope has no need of advice from a poor idiot like me.”

Journet wrote back advising Maritain to “save his strength for what concerns the faith and the truth that is closely connected to it” and to “leave all this to the omnipotence of God.” Maritain agreed, expressing relief (“The question of birth control is none of my business!”), yet he found it impossible to drop the subject, adding at the end of the same letter a “final word,” hand-written instead of typed, in an attempt “one last time to defend my idea concerning birth control.” Again he insisted to Journet that the rhythm method was no better morally than the pill, because “mental calculation with a view to avoiding that possible effect (by choosing periods of sterility for the opus) is something just as ‘artificial’ with regard to nature as a medication that modifies conditions prior to the opus but in no way affects the latter itself.” He felt convinced of this. “But,” he added, “I don’t want to talk any more about it.”

And he didn’t, for more than a year anyway. On July 25, 1968, Humanae vitae was promulgated. In his notes Maritain called it “a very beautiful document, very noble and very human,” yet added that “it causes me pain and disappoints me.” And further: “What a shame that it has come out after the Credo.”

Just four weeks earlier, Paul VI had proclaimed the Credo of the People of God. The pope had asked Journet to help him prepare the text, and when Journet in turn asked Maritain for help, Maritain produced a text that Paul VI adopted almost word for word. Maritain feared that the Credo would receive the same contested reception Humanae vitae did. And indeed, on August 24, Journet wrote to announce that he had fielded a request, “par ordre supérieur,” for an article that would appear in L’Osservatore Romano defending the authority—and hence the competence—of the Holy Father in Humanae vitae. This request, Journet noted, came indirectly, via two messenger monsignori, from the pope himself. “Jacques,” he begged his friend, “if you have some point to suggest to me I would bless you!”

Maritain quickly came to the aid of his friend with a long letter. In it, he declared himself conflicted about the encyclical, calling it “admirable in tone, in elevation, in charity, and in courage,” yet confessing that its arguments “do not hold close enough to what is real and concrete,” and thus left him “not satisfied.” As for the article Journet was to write, Maritain advised him “as much as possible refrain from discussing…the subject itself of Humanae vitae.” Attempting to defend the encyclical point by point, Maritain warned, “would only redouble the sarcasms it has attracted.” He advised Journet to speak instead as “a theologian of the church, and to the general question of the authority of the pope.”

Noting what he called “the absurdities spouted off by the priests who are rising up against the encyclical,” and lamenting “a spirit that is antipapism and disdain for obedience in general,” Maritain encouraged Journet to push back hard (“Don’t go into this fight pulling your punches!”). The heart of the article, he said, should be a “theological exposé,” not a scientific treatise. “The pope is the successor of Peter and doesn’t have to consult anyone,” Maritain reminded his friend. “Let your article be an implacable defense of the primacy of the pope.” Whatever Maritain’s personal reservations about Paul VI’s arguments in Humane vitae, he pledged obedience as a Catholic. “I am led to believe that the conclusions of the encyclical, condemning the pill, etc., have the value of infallibility and oblige the conscience in the name of theological faith itself.”

In preparing his defense of Humanae vitae, Journet followed Maritain’s advice to the letter. He did not discuss the subject of the encyclical, but held fast to the issue of the pontiff’s authority to decide it. After citing the scriptural foundations for the pope’s supreme authority, Journet discussed the levels of that authority: personal or collegial; solemn or ordinary; proclaimed by mediation through delegated organs or immediately through encyclicals. Journet’s conclusion was that “one thing is certain: the ordinary magisterium of the sovereign pontiff is in full force here. The theologian who reflects on the gravity of the cause, on the level of light to which it has been lifted to be made clear, on the precision and the certitude with which the response has been given, will be able to think that he finds himself…in the presence of a moral doctrine definable later on and capable of rising one day to the level of an assent of divine faith.”

That both Journet and Maritain assented so quickly and completely is not surprising. Maritain’s conversion to Catholicism was not the result of a rational progression, after all, but rather was equivalent to being “turned inside out like a glove,” as he had written in describing the conversion of Jean Cocteau. And so while he felt that the encyclical should not have been promulgated, Maritain wrote that his “spirit of faith” obliged him to accept what his human reason led him to reject. Journet, for his part, was a theologian of the church and a defender of its authority, and as such wanted to put an end to the unsettling controversy over the authority of Humanae vitae. Defending the encyclical, he acknowledged that “the preambles and the arguments proposed in the encyclical can certainly be discussed, weighed, subjected to deliberation.” And why could they be discussed? Because, he went on, “they have no other object than to prepare the conclusion; they are not its basis.”

For many people, however, legitimate discussion, weighing, and deliberation imply the possibility of change, which in turn implies that the conclusions may not be infallible pronouncements but reformable ones. This controversy has perpetually unsettled the church—and continues to do so to this day—but Journet seems to have felt that a more authoritative papal proclamation, under the supreme personal authority of the sovereign pontiff in a solemn declaration, would bring an end to the turmoil. He looked forward to “a point of moral doctrine” that would be “ultérieurement définissable,” definable later on, and requiring the “assent of divine faith.”

That was in 1968. Thirty years later, Pope John Paul II, in his apostolic letter Ad tuendam fidem, would introduce a new category of teaching, called “definitive,” explaining that such a teaching, though not infallible, was nevertheless irreformable. Journet’s hope for the “ultérieurement définissable” shows just how prescient he was, and reminds us that the discussion of “definitive teachings” was very much in the air at the time of Humanae vitae. From Catholics, such teachings would require obsequium—this word has many meanings: loyalty, respect, obedience—as well as a “submission of intellect” and an “assent of faith.”

Maritain died in 1973, and Journet two years later. With loyalty and respect, both of these formidable thinkers gave their assent of divine faith—and submitted their intellects—to the teachings of the encyclical. We will never know whether they accepted those teachings as irreformable, as the status of “definitive teaching” was not then settled, and is still not. How can a proposition that is not infallible—such as the conclusions of Humanae vitae—be nonetheless irreformable? One suspects that many more letters remain to be written, and words spoken, before that question is answered.

Related: Indefensible: Moral Teaching after 'Humanae Viate,' by Michael Dummett