Throughout most of recorded human history, marriage was a means for consolidating wealth, improving social status and creating a miniature labor force from the fruits of one’s loins. Marriage contracts detailed the exchange of money, land and goods and the obligations of each party; there was little or no expectation of romance. Divorce was rare, because few individuals (women in particular) could prosper outside the institution of marriage.

Sometime around the 14th century, marriage vows came into vogue in England and France, and in the 16th century, the word “love” began to crop up in those vows. Fast-forward to the year 2014, and most American wedding vows contain some version of “I promise to love you forever.”

In the course of just one century, marriage has evolved from an economic institution to a vague public declaration of love. According to the Pew Research Center, 88% of Americans cite love as the most important reason for marrying, rating it as being more important than financial stability or companionship. Marriage contracts no longer detail how many cows or acres of land are to change hands. Of course, for high-net-worth individuals, prenuptial agreements are still used to detail the flow of wealth in the event of marital dissolution. These agreements are rare, however, and they are called “prenuptial” for a reason: Nuptial agreements are no longer supposed to have anything to do with money (pdf). Instead, the promise of love is now considered to be the core of the contract, even though it’s rare for most marriages to live up to that promise for a lifetime.

If the modern wedding contract states or implies undying love, how do we reconcile that with the reality of our relationships? Nobody would ever sign an employment contract that said, “I not only promise never to leave this job, but I promise to be equally enthusiastic about working here for the rest of my life, no matter how this job evolves and no matter how much I change as a person.” Yet this is more or less what most of us do when we get married. We promise that we are going to continue to feel the way we do today in perpetuity, even though experience teaches us that our feelings about most things change over time.

A good contract is specific, sets realistic goals, and is enforceable. “I promise to love you forever” has none of those attributes. It is in nobody’s power to promise to feel a certain way 20 years hence, and no family court judge in the country can say, “Edna, you promised to love him forever. Forever isn’t over yet, so get back in there and looooove him!” Moreover, the test of a good contract comes not when it is written, nor when the signatories are happy; the value of a contract only becomes clear when it is challenged. “I promise to love you forever” says nothing about what should happen if the love goes away.

If we took a more clear-eyed view of the modern marriage contract, what might it look like?

“I, ____________________, do promise to act as though I love you, __________________, for as long as I shall live. I promise not to leave you under any circumstance, no matter how miserable it makes me to stay with you.”

This is a better contract, because it promises something that is actually deliverable. It is possible to act lovingly without feeling love. It is also a more specific contract, because it clearly states that there are no circumstances under which the marriage would end. The obvious problem with this contract is that very few people in modern western society would sign up for a potential lifetime of misery. Even when two people are in the most fevered throes of love, this does not seem like a smart promise to make.

Here is another example:

“I, ____________________, do promise to do my utmost to love you, __________________, for as long as we are married. I promise that if a time comes when I do not love you, I will do everything in my power to try to rekindle that love. If I become convinced that I cannot regain my love for you, I will tell you promptly and end our marriage as elegantly as I can.”

This contract is realistic, and it provides for the most important contingency, the end of love. It sets the expectation that the marriage may not last forever, and it also promises civilized behavior in the event that the marriage does not last. This contract is far superior to “I will love you forever,” and yet it is unlikely to be adopted any time soon, because it is so unromantic.

Our society clings to wedding vows that are vague and unenforceable because we are a culture of hopeless optimists and romantics. We want the end of every love story to be “happily ever after,” and we certainly don’t want to acknowledge the possibility of error or failure on our wedding day. Perhaps, then, everyone should have a prenuptial agreement, not to address division of assets, but to delineate the circumstances under which each party believes the marriage could or should be dissolved, and to set out behavioral expectations for that unfortunate circumstance. Such an agreement could put divorce lawyers out of business, but it could also prevent a great deal of confusion, disagreement and heartache when “I will love you forever” turns out not to be true.