Summertime means wedding time. Wedding time means an occasion to reflect upon relationships. What makes for a lasting marital commitment? What can I learn from my friends’ examples? What connections exist between premarital relational practices and how a couple fares in married life?

So reflecting I am forced to confront the problem of cohabitation. I know couples who are cohabiting, or who are struggling in the aftermath of a broken cohabitation, or who have cohabited and are apparently happily married. The culture assumes cohabitation is normal, yet my faith and my instincts tell me that it is seriously wrong.

My view against cohabitation boils down to three convictions: that cohabitation (as it’s typically understood) is always wrong; that it does not help couples discern “marital compatibility,” as it’s often thought to; and that a healthy love for marriage usually prudentially defeats reasons for even uncommonly good cohabitations.

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First, cohabitation is wrong simply by being a nonmarital sexual relationship. Sex is for marriage. The magnitude and meaning of one corresponds to the other and is not right without it.

Second, cohabitation is not a reliable source of marital discernment. A helpful USCCB resource notes (using figures from the 1990s) that up to 30 percent of cohabitors intend never to marry, and 20 percent of cohabiting partners disagree about whether or not they intend to marry. So about one-third of cohabiting couples have no intention of marrying, of making any public commitment to each other that transcends their individual desires. The arrangement is one of mutual self-service. Also, roughly one-fifth of all cohabiting couples lack shared goals and expectations and also apparently lack communication about the fact that they don't share goals and expectations. Cohabitation in these instances won’t help couples know whether to marry, and if they do, to be good spouses.

Still, if these rates are similar today, a majority of cohabiting persons do intend to marry. Why do they cohabit, then? Many see cohabitation as “prophylaxis” against divorce, as clinical psychologist Meg Jay put it in her 2012 New York Times op-ed on the topic. Can it help them discern whether their marriage will survive?

Cohabitation cannot be a prophylactic for a few reasons. First, by its intended purpose it flouts the central marital feature of permanence. Those who cohabit out of a desire to screen for various forms of compatibility, to aid discernment vis-à-vis this particular person, do so on the understanding that if things go awry, then the couple will split, and thereby head off what would be a more painful split (divorce) down the road. Permanence is meant not to be integral to cohabitation, and often trains couples against permanence in “marital” settings.

Of course, if one envisions marriage to be as easily dissoluble as cohabiting couples understand their domestic arrangements to be—and some people do see marriage that way—then this line of reasoning doesn’t apply. Then again, if this is the case, it undercuts the same line of thinking on which cohabitation is thought to be good preparation for more lasting marriages. Even so, the formation of habits of seriously unethical choices—such as nonmarital sex—warps discernment powerfully; couples sleeping together may marry for feelings of false intimacy or compatibility, when they never would otherwise.

Second, we can say further that cohabitation tends to teach the reverse of the true link between feelings and action in marriage.

One can’t promise what one can’t control. The lessons of Hollywood romantic flicks aside, one can’t ground a promise—or a vow or binding commitment—in one’s feelings because feelings are fleeting and always originate and transpire to a great extent outside one’s direct control (though we can train ourselves to have certain feelings—more or less and over time—even if we can’t just will to have them).

Marital vows, like all promises, are commitments to do and not do certain things, not to feel and not feel certain ways. But the cohabiting couple doesn’t easily realize this; they may miss this causal relationship, seeing only its inverse. Commitments to action affect one’s feelings to an extent and also affect how one reacts to, or acts upon, one’s feelings. A commitment to spousal fidelity entails, at least for the person striving to live out that commitment, combatting whatever feelings might tempt him toward unfaithful actions (even if only deliberate mental entertainment), and will lead him to locate the origins of those temptations and avoid them or else confront them.

Cohabiting couples are liable to think that where marital commitment is concerned, feelings should dictate actions: One renders one’s marital commitment conditional upon a deeply felt sense of compatibility in an ostensibly marital setting. Now, to an extent feelings should dictate actions. But the cohabiting setting cannot be marital because permanence is not a part of that couple’s self-understanding. It doesn’t surprise me that those who see cohabiting to be a realistic prophylactic against divorce find themselves unable to transition easily into living a permanent union after the wedding, and thus divorce at higher rates than those who do not cohabit. (The divorce rate rises proportionally with the greater number of one’s prior cohabiting relationships. We should expect this if cohabitation trains couples against permanent commitments, skews the relationship between feelings and actions in marriage, and encourages “sliding into” rather than “deciding on” relational milestones.)1

Dating is good for discerning marriage, though like typical cohabitations it doesn’t carry the expectation of permanence. What explains this difference?

Many couples mean cohabitation to correspond more or less to married life: They share all the blessings and burdens of domestic life, as married couples do, and make many decisions as if they were married. Dating does not and isn’t meant to resemble marriage in this way; the couple understands the many practical differences between dating and marriage and don’t see the former as a “simulation” of married life.

Because cohabitors are "testing" marriage with a firm expectation of non-permanence in an environment that commonly closely resembles marriage practically, enduring in that same environment will be all the more difficult because of the practical similarities between cohabitation and the commitment wherein permanence is expected: marriage.

But the dating couple harbors no pretenses of sharing the domestic life proper to marriage. As such, the dating couple's expectation of non-permanence won't hinder (or at least nearly so powerfully) their ability to navigate well a permanent domestically shared household down the road. We can say of cohabitation and nonmarital but “marriage-like” domestic arrangements that the more closely a relationship resembles married life in this respect, the more detrimental to married life those relationships will prove for the persons involved, whether they marry each other or go their separate ways.

Finally, a healthy love for marriage usually will prudentially defeat reasons for even uncommonly good cohabitations.

Surely there are couples who are deeply committed, intend to marry soon, make relational decisions conscientiously, and also seek to avoid sex outside of marriage? Might not they be able to live together—say, due to scheduling conflicts between move-in dates, job beginnings, graduations, and so forth—when the alternatives involve significant costs?

I would say no. For one thing, the erasure of domestic boundaries strongly encourages the erasure of boundaries of sexual intimacy. The domestic trappings of married life will encourage a possibly subconscious but nonetheless action-guiding view that the couple is “all but married.” In short, cohabitation even for couples wanting to be chaste and who intend to marry soon is a persistent occasion of temptation toward fornication, and as such the couple has a serious duty to avoid it.

In some circumstances, a couple might seek living arrangements that involve other roommates in order to ease economic burdens and shift the general atmosphere of the household away from “cohabitation”; doing so might make the cohabitation even more dissimilar to typical cohabitations and their detrimental aspects.

There might be proportionately serious countervailing reasons for cohabiting in this atypical sense—i.e., couples who are deeply committed, intend to marry soon, make relational decisions conscientiously, seek to avoid sex outside of marriage, and nevertheless for some reason choose to cohabit—that offset my suggested reasons against doing so; in any event, the desire for marital discernment won’t be one such reason, since the couples in question have already made plans to marry.

Even if such reasons can be found, we can still say that all cohabitations as typically understood are wrong. They involve seriously unethical habits of action. They tend to skew and inhibit, rather than aid, marital discernment. They tend to make couples less deliberate about goals and boundaries, train them against marital permanence, and encourage them to embrace an unsound link between feelings and action in marriage. This isn’t to say that couples who cohabit don’t or can’t go on to marry and to be good and faithful spouses, but cohabiting does make that harder and less likely. A healthy love for marriage (the human good), marriages (in the concrete), and marriage culture will usually defeat even those cases that don’t fit the common mold.