1. Introduction

I could never conceive or tolerate any Utopia which did not leave to me the liberty for which I chiefly care, the liberty to bind myself. Complete anarchy would not merely make it impossible to have any discipline or fidelity; it would also make it impossible to have any fun. – G. K. Chesterton

Each person has a personal cross to bear, and each is in many ways a cross to others. Much mutual charity, humility, and forgiveness are demanded of each. If this is all true in the family, it is even more true in society at large. – Michael Novak

Contracts are essential to a functioning society. They help parties reduce the costs and risks of trade, facilitate long-term investment, increase specialization, and foster cooperation. The even-handed enforcement of contracts is rightfully one of the key aspects of the rule of law that researchers consider when measuring economic freedom (Gwartney 2024). Persons in a society without the ability to enter and be bound by their voluntary contractual agreements would be significantly impoverished in both a material and spiritual sense. While this is true of commercial contracts, it is even more true of marriage.

While marriage is much more than a contract, for economists, it is at least a contract. Thus, many of the things we have learned about contracts and their role in society may be fruitfully applied to marriage. Scholars have even suggested that contract law emerged from the Church’s involvement in marriage during the early medieval period (Berman 1983). Marriage might even be thought of as the ur-contract.

There are many different understandings of marriage, and each of these implies different contractual features. Perhaps the most common historical view of marriage is that it creates an alliance between families. Understandably, then, the father’s permission was required in many contexts. In the contemporary United States, spousal consent is dispositive—which means that only the betrothed need to individually consent—but each of them is also free to leave the marriage when they choose.

Since there are many possible marriage contracts, which one is fitting for a free society? To answer this question, it is useful to return to the sixteenth century, at the Council of Trent (1545–1563), when the Catholic Church outlined a marriage contract that is unique with regard to both the historical and the modern models of marriage. This particular marriage contract had a serious role to play in the development of four primary liberal institutions: (1) a free marriage market, (2) a fair and impartial rule of law, (3) a free economy and civil society, and (4) a limited but effectual state. But first, this peculiar marriage contract warrants careful analysis.

2. The Economics of the Tridentine Marriage Contract

On November 11, 1563, during the twenty-fourth session of the Council of Trent, the decree on marriage was approved. The Council issued twelve canons on marriage as solemn anathemas (anathama sit) and renewed or reformed several marriage practices in the following chapters. Three features emerge from these statements: (1) a marriage bond that is perpetual, meaning it can only be dissolved through the death of one of the spouses, (2) a marriage bond that is established by the free consent of both spouses, and only theirs (rather than including parents, political authorities, etc.), and (3) a marriage bond that is celebrated publicly, including the presence of the local parish priest and at least two witnesses. This constellation of features may be referred to as the Tridentine marriage contract for short. Although its elements were present and developing in the centuries prior, the statements at Trent mark the sharpest distinction and strongest enforcement of this peculiar approach to marriage.

2.1. Perpetual Bond

The oldest and most distinctive feature of the Tridentine marriage contract is the doctrine that, to borrow earlier language from the Council of Florence (1431–1449), “the bond of a legitimately contracted marriage is perpetual.” Once validly contracted and consummated, the marriage contract can only be dissolved by the death of one of the parties. To use a careful phrase from Brugger (2017), “consummated sacramental marriages are extrinsically or absolutely indissoluble” (p. 6). While there are two notable exceptions for marriages in which one or both of the parties are not baptized, all valid marriages remain intrinsically indissoluble, meaning that later actions taken by those who contracted the marriage cannot dissolve the union. Note, however, that this does not mean the spouses cannot live apart or be separated. The Council of Trent expressly declared that there are “many reasons a separation may take place between husband and wife with regard to bed and with regard to cohabitation for a determinate or indeterminate period” (Canon 8). Finally, it also left space for an annulment process, by which a marriage thought to be valid could be shown to have fallen short of at least one of the essential required elements, such as the free exchange of consent. While this may look like a divorce or separation, it is not. Rather, it is a declaration of nullity following a process of investigation by the Church tribunal.

It is important to emphasize the uniqueness of the doctrine that marriage is a perpetual bond. For many other religious traditions, as with Judaism and in the Orthodox churches, the marriage contract can be dissolved in the case of adultery. Brugger (2017) emphasizes that the position of the Council, not allowing an exception for divorce, was politically inconvenient. Such an interpretation of Scripture was only possible because “the dissolution of political unity in the Western part of the Empire from the sixth century left the Latin church much less encumbered by imperial interference” (Brugger 2017, 4).

2.2. An Economic Analysis of a Perpetual Bond

From the economic perspective, a marriage contract primarily functions as a commitment device for the spouses (Matouschek and Rasul 2008). Successfully living together requires repeated cooperation from both spouses (e.g., “if you cook the dinner, I’ll wash the dishes”), but such cooperation is costly for each spouse. If the cooperation is expected to end in the future (e.g., one night I’ll decide I’m too tired to wash the dishes), then the other spouse faces an incentive to “defect,” or not to cooperate in the period before (i.e., not to cook the dinner). This causes cooperation to unravel, because neither spouse can fully trust that the other won’t be looking out for their own interests over those of the couple. People use marriage to bind their partners and their future selves to their promises.

Relatedly, a marriage contract must also be able to encourage specific investments, meaning investments that have little value outside of that relationship. Children can be thought of as a specific investment. More than anyone else in the world, your spouse values the investments you make in your children. There is also a timing problem that makes cooperation necessary, since each parent invests more in the children (at the expense, perhaps, of market income and career experience) at different years of their life or even at different times of the day. To sum up, a perpetual bond gives each spouse the security needed to fully cooperate and invest in their specific marriage and household, knowing that they will both enjoy the fruits of that investment into the future.

Human nature is frail and fallen, and such a strong contract may become an occasion for tyranny. The Council urged the separation of spouses under certain conditions (e.g., spiritual or physical danger). Crucially, though, these circumstances do not break the marriage contract, and so remarriage by either spouse remains off the table as long as the other is alive. We can think of this as a “noncompete” clause—the payoff to leaving one’s marriage is vastly reduced if neither spouse can remarry and so separating is likely to only occur in serious circumstances.

Finally, there are two cases where the marriage contract may be dissolved by an extrinsic authority—the Pauline Privilege and the Petrine Privilege—in which one or both of the parties are not baptized and thus had not contracted marriage with the same understanding and expectations as the Church. These may be granted only if one of the parties wishes to enter under the authority of the Church (meaning, conversion or remarriage) without cooperation from the other spouse. Still, if there is a valid marriage between two baptized persons, not even the pope can dissolve it.

All marriage contracts involve some form of consent between (at least) two parties. The key question is: Whose consent? Throughout history, marriage agreements often involved the parents (usually fathers) of the spouses, or even a political authority. However, the specific understanding of marriage crystallized by the Council of Trent requires the free consent of both spouses and explicitly prohibits family members or political authorities from arranging a marriage to achieve their own ends. Even in modern marriage preparation in the Catholic Church, couples are taught that “the consent makes the marriage.” This is such a strong belief that the couple is prohibited from consuming any alcohol on the morning of the wedding or engaging in any behavior that would jeopardize the freedom of their consent and be later grounds for an annulment.

The Council also outlined limits to the consent of potential spouses. For instance, even if both parties were consenting, marriage could not be contracted between cousins (of varying degrees). The Council also strongly condemns even “consensual” concubinage in particularly strong language:

It is a grave sin for unmarried men to have concubines, but it is a most grave sin, and one committed in singular contempt of this great sacrament, when married men live in this state of damnation and have the boldness at times to maintain and keep them in their homes even with their own wives (Chapter VIII).

For a marriage to be valid, the spouses must be consenting to lifelong marriage with this person, to whom they did not have existing ties of affinity and neither of whom has already contracted marriage with another.

Consider the economic rationale for the requirement of spousal consent, as well as its limits. First, consent solves important information and incentive problems present in the marriage market by putting the person who stands to lose or gain the most from a marriage in charge of the decision, i.e., finding their spouse. While a parent or political authority may have other goals in mind (as the Council writes, “Worldly inclinations and desires very often so blind the mental vision of temporal lords and magistrates”), the spouses are more likely to be focused on the success of the marriage itself. This would increase the time or effort spent searching for one’s spouse and make it more likely for the match to be “high quality,” which also would benefit the children.

Second, the requirement of consent also makes competition over spouses a relatively peaceful affair. Instead of kidnapping a bride, for example, one would have to persuade her by performing courageous deeds for the community or exhibiting exceptional generosity. This would also serve to increase the quality of the marriage match—this time through the channel of better information—while not expending valuable resources in violent conflict. Third, if the death of a spouse is the only way to remarry, then there is the obvious moral hazard problem of people killing their spouses (so-called “Italian divorce”!). Free consent reduces this possibility.

Finally, the limits on consent can be understood from the economic perspective as well. Consent in marriage could only be given to one person who was not already married. While it may be in the private interest of a woman to attach herself to the household of a “high-status male” (to borrow the language of evolutionary psychology), it would not be beneficial at the societal level. There would be many men left without a wife, but perhaps more crucially, many children would be left without sufficient investment from their father due to his split attentions. The ban on cousin marriage reinforced the importance of consent, doubly prohibiting extended families from arranging marriages for their own interests.

2.5. Public Celebration

The third and final aspect of the Tridentine marriage contract is the requirement of a public celebration, specifically, that marriage be conducted in the presence of the spouse’s own parish priest and two or three witnesses. This logically builds upon the other contractual features previously mentioned: To ensure a successful lifelong marriage, one would want both spouses to enter it freely, but to establish a legal record of their free consent, one would need witnesses.

2.6. An Economic Analysis of Public Celebration

The Council spilt much ink emphasizing that it is not just any priest, but one’s own parish priest, that ought to preside over the marriage celebration. Far from being an obscure requirement, this rule ignites the drama of the classic Italian novel by Manzoni, I Promessi Sposi (The Betrothed). But why would it matter to have one priest versus another? At a time when geographic mobility was much lower than today, so that the couple could reasonably be expected to live and raise their children within a particular parish’s bounds, this draws a relatively impartial third party into the marriage contract who is also invested in its success. Recall that priests are expected to be celibate, so this preserves them from additional conflicts of interest with regard to how marriage contracts are enforced. If the couple is able to successfully build a home together, the parish and the priest benefit from this. He thus faces a greater incentive, relative to another priest, to dutifully prepare the engaged couple for their life together. He is also most likely to be aware of any impediments to the marriage.

Witnesses solve information problems for both society and the Church. First, they can testify that agreement was valid. In this case, the priest may play the role of an impartial, tie-breaking witness should the marriage ever need to be investigated in an ecclesial court. Second, the need for witnesses protects against the threat of adverse selection that arises from the emphasis on consent only of the spouses. We can see this at work when the Council sternly cautions against the marriage of a vagrant who might be traveling to avoid his previous marriage and its attendant responsibilities. The requirement to find witnesses implies that the couple needs not only to convince their local priest but also two other adults that this marriage is a good idea.

3. The Marriage Contract for a Free Society

A society could not be called free if it offered only economic freedom or political freedom. A free society needs a marriage contract that is strong enough to support the institutions of liberty but one that is not so strong as to overpower the freedom of the individual. In short, the marriage contract must underpin four key aspects of society: (1) a free marriage market, (2) a fair and impartial rule of law, (3) a free economy and civil society, and (4) a limited but effectual state. The Tridentine marriage contract, for all its peculiarities, could do just that.

3.1. A Free Marriage Market

It is well known that children thrive in a nuclear family. As Kearney (2023) points out, in all of human history, no one has found a better institution for providing children with the resources they need to flourish than the two-parent household. Nuclear families did not emerge on their own, however. In many ways, they presuppose a free marriage market.

A free marriage market is one in which potential spouses compete for each other’s affection, and only the consent from individual spouses is required for a marriage contract to be established. In the terms of economics, this market would avoid the principal-agent problems present when more parties are involved and encourage the potential spouses to engage in optimal search. A free marriage market isn’t lawless. The terms of the marriage contract would be upheld and enforced in an even-handed manner, at least until both spouses desired it to end, or clear fraud or danger was present. A free marriage market was, in short, exactly what emerged from the Tridentine marriage contract.

A marriage contract like that from Trent is certainly not required for the formation of nuclear households, but another contractual form usually requires some additional features that will make the agreement self-enforcing. By establishing and enforcing marriage as a lifelong contract, the Council reduced the need for self-enforcement, which was expensive and thus excluded potential couples. Effectively, it opens up the possibility of a stable marriage to couples and their children regardless of their socioeconomic status. Recent research illuminates this mechanism in the context of the contemporary United States. Lafortune and Low (2023) point out that the presence of a valuable asset—such as ownership of a house—can act as “collateral” in a marriage, making it more binding than would otherwise be the case. They show that spouses who own homes together tend to specialize more—one perhaps focused on managing the home, while the other is focused on earning a market wage—and divorce less, thereby gaining from their continued cooperation. Poorer households, on the other hand, are less able to sustain such cooperation because they lack collateral. By making the stability of marriage available to rich and poor families alike, the Council increased the possibility that children from all backgrounds would grow up with the benefits of a two-parent home. Channeling Michael Novak, it might be said that children can then also see what is possible for a free society, that it is possible to keep one’s promises and to cooperate constructively with another person over a very long time horizon.

But what about the cases in which the Council allows spouses to separate, effectively breaking apart a nuclear family? A free society is also one that protects the vulnerable. The ability to separate from a spouse ultimately safeguards the well-being of vulnerable spouses and children. By allowing for separation but not remarriage, the benefit of separation is so drastically reduced that only those who desire the separation for the separation’s own sake will do so. On the other hand, the annulment process allows for mistakes to be corrected and encourages the couples to follow a standard rubric for the celebration of marriage, making it less costly to enforce the marriage contract. Importantly, a free society is one with the freedom of religion. Both the Pauline and Petrine Privileges dealt with such cases of freeing a spouse from one who did not share or tolerate their religious faith.

3.2. The Rule of Law

A free society requires a fair and impartial rule of law. Just as with a free marriage market, a rule of law is influenced by the structure of the families within its ecosystem. The Tridentine marriage contract had both direct and indirect impacts on the development of such a rule of law.

Directly and practically, the Church had to work through numerous legal problems to stipulate what counted as consent in a marriage. As Berman (1983) documents:

The rules concerning consent to a marriage were developed into a whole body of contract law. The consent must have been given with a free will. A mistake concerning the identity of the other party, or a mistake concerning some essential and distinctive quality of the other party, prevented the consent and hence nullified the marriage. Duress also nullified the marriage by interfering with the freedom of consent. It was also ruled that a marriage could not be validly contracted under the influence of fear or fraud. Here were the foundations not only of the modern law of marriage but also of certain basic elements of modern contract law, namely, the concept of free will and related concepts of mistake, duress, and fraud (p. 228).

The canon lawyers even solved a problem that had stumped the Roman jurists: the problem of mistaken identity (which they solved by asking whether the marriage would have been contracted if the parties knew the truth). As contract law improves, so do the possibilities for trade and prosperity in a free society.

Moreover, the Tridentine marriage contract had an indirect impact on the rule of law by reducing the level of conflict in society, which is costly in that it draws resources away from other productive uses. In particular, the requirement of consent by spouses meant that persuasion, or courtship, became the means by which one finds a marriage partner. By encouraging high-quality matches, it also reduced the potential for conflict within marriage that would need to be adjudicated by a court. As economists like to point out, the rule of law is a scarce good, so it must be economized by a society. If a marriage contract can reduce conflict, then more resources are available to devote toward resolving disputes in other areas.

Finally, the Tridentine marriage contract led to a fairer rule of law, particularly in its treatment of women. Not only was kidnapping a bride off the table, but becoming a bride at a very young age was also prohibited, since one had to be old enough to legally give consent. In fact, female age at marriage has proven to be such a strong indicator for female autonomy that it is used frequently by economic historians. To quote Berman again (1983):

In pagan cultures in which polygamy, arranged marriages, and oppression of women predominated, the church promoted the idea of monogamous marriage by free consent of both spouses. In the West this idea had to do battle with deeply rooted tribal, village, and feudal customs. . . . [C]anon law offered considerable protection—as contrasted with the folklaw of the society in which it first developed—to the female partner in the marriage. (pp. 226–229).

It is little wonder that wealthy women flocked to Christianity in these contexts, as Stark (1995) and Holland (2019) have pointed out.

3.3. The Freedom of Association

The adoption of the Tridentine marriage contract also laid the groundwork for the freedom of association in at least three ways. First, as mentioned previously, the feature of consent encouraged a norm of persuasion and optimal search by spouses, which allowed for unconventional choices. The development of a free marriage market became a new space where young adults (or widows and widowers) could peacefully engage in the important work of finding someone to marry. Second, in contrast to Roman law and prevailing folk customs, it did not prohibit marriage across class lines. This fostered a degree of social mobility, as did the spread of the nuclear family. Finally, the Council defended the Church’s ongoing ban on cousin marriage, which meant that individuals would need to reach outside their kin networks to find potential spouses. All of these features extended the division of labor, specialization, and trade in society, playing a key role in what economists sometimes called the Great Fact, that is, the enormous growth in economic prosperity experienced by Western Europe.

The importance of the ban on cousin marriage (which evidence suggests was genuinely enforced) has been the subject of a burgeoning literature which identifies this as the decisive break between the West and the rest of the world. For example, Heinrich (2020) documents the psychological and cultural differences between populations with extensive cousin marriage and those without. Societies with cousin marriage emphasize family connections and loyalty to one’s kin group, while those with low rates of cousin marriage care more about individual intentions and identify more as members of voluntary groups. Schulz (2022) has also shown that by breaking up kin networks, the Church’s ban on cousin marriage made room for a large range of democratic associations. While countries with high rates of cousin marriage tend to be autocratic with a weak rule of law, countries with weaker kin networks tend to have more democratic institutions and voluntary associations—what we might call “civil society.”

3.4. A Limited State

Finally, the Tridentine marriage contract limited state power in two ways: (1) By encouraging stable, two-parent homes it reduced the need for social services that would substitute for spousal or parental investment, and (2) it placed the marriage contract under the jurisdiction of the Church, primarily, limiting the state’s power to change its features to serve political ends.

Since the first limit has been discussed previously in this paper, it is worth analyzing the second in more detail. In Chapter IX, the Council of Trent declares:

Wherefore, since it is something singularly execrable to violate the freedom of matrimony, and equally execrable that injustice should come from those from whom justice is expected, the holy council commands all, of whatever rank, dignity and profession they may be, under penalty of anathema to be incurred ipso facto, that they do not in any manner whatever, directly or indirectly, compel their subjects or any others whomsoever in any way that will hinder them from contracting marriage freely.

As one might imagine, governments have not much liked this idea of marriage freedom. The ruling elites prefer to change the features of the marriage contract in response to their changing needs. In Soviet Russia, for example, just one year after the Bolsheviks took power, they ratified the 1918 Code on Marriage, the Family and Guardianship which introduced no-fault divorce, abolished adoption, and banned religious marriage (among other things). This was done, in part, because the state needed women to work in the factories rather than at home.

Fewer than two decades later, however, the Family Code of 1936 overturned nearly all its previous policies and began to spread pro-family, pro-natal propaganda all over the country in an attempt to raise drastically low birth rates and manage the large numbers of orphans. It kept the ban on religious marriage, however. Piano and Flowers (2025) point out:

It is not unexpected that divorce rates should rise and fertility should fall once the Soviet Union legalized unilateral divorce and abortion. What does present more of a puzzle to social scientists is the fact that the Soviet Union could not reverse these trends, even as legal efforts were made to raise the price of divorce to prohibitively high levels and to penalize couples without children. The missing piece in Soviet policy that had been present in religious marriage—specialized third-party enforcers of the marital contract—can help explain this failure.

Specialized third-party enforcers of the marriage contract provide stability to spousal expectations, in contrast to the changing features of state-led marriage contracts. The Tridentine marriage contract provided couples with this specialized enforcement, their local priests and church community, who would also safeguard the family against the threat of totalitarianism. Years later, Pope Leo XIII’s encyclical Rerum Novarum would remind the world of the Church’s position on this matter:

No human law can abolish the natural and original right of marriage, nor in any way limit the chief and principal purpose of marriage ordained by God’s authority from the beginning: “Increase and multiply.” Hence we have the family, the “society” of a man’s house—a society very small, one must admit, but none the less a true society, and one older than any State. Consequently, it has rights and duties peculiar to itself which are quite independent of the State. . . The contention, then, that the civil government should at its option intrude into and exercise intimate control over the family and the household is a great and pernicious error (paras. 12 and 14).

This limitation of state power preserves the integrity of the marriage contract and allows the state to focus on supplying the services for which it has a comparative advantage in a free society, rather than competing with religion. To make this effective, however, the Council had to set up a marriage contract that would allow family members to freely depend on one another, rather than on the state, for certain goods and services for which the family has a comparative advantage in a free society, namely, the rearing of children.

4. Conclusion

The family is the nexus for freedom in society. It is where children are cared for and learn to cooperate with others, where husband and wife keep their promise of “free trade” with one another, and where all practice the “liberty of dependence” (Pakaluk 2016). These benefits do not emerge from just anywhere, however. The long-term cooperation necessary for a successful marriage requires particular contractual features. The Tridentine marriage contract, with its unique threefold emphasis on dispositive spousal consent, indissolubility, and publicity, could establish such a flourishing family life, and in doing so, laid the groundwork for the liberal institutions we know and love.