Sex is often treated as one of the least profound aspects of enduring romantic love, yet sexual infidelity is experienced as one of love's deepest violations. How can we explain this paradox?
The Paradox of Sex
The paradox of sex in romantic relationships is that its positive contribution to a flourishing, enduring relationship may sometimes seem limited, providing largely momentary physical pleasure. Yet when it violates an exclusive bond, sex can carry enormous destructive power. Why does something often dismissed as "just sex" become the ultimate romantic betrayal?
Romantic love rests on two major evaluations: (a) a partner's attractiveness and (b) the praiseworthiness of the partner's traits and achievements. The first is typically expressed through sexual desire; the second deepens friendship, caring, and admiration. Although these evaluations are distinct, they often reinforce each other. Attractive partners are frequently perceived as possessing more admirable qualities, while admired partners often become more attractive. This duality reflects the ambiguous nature of sex: It may provide immediate physical pleasure while also strengthening a profound emotional bond.
To understand this paradox, I examine five related issues: the ambiguous nature of sex, the roles of change and familiarity, the distinction between making love and having sex, the intimacy continuum, and sexual afterglow.
The Ambiguous Nature of Sex
Sex can be viewed as serving two primary functions: bodily pleasure and relational connection. From the first perspective, sex need not threaten romantic love. Hence the familiar claim: "I had sex with someone else, but I still love you." Yet sex can also embody intimacy, exclusivity, desire, and belonging.
A sexual interaction may be physically brief yet psychologically significant. A kiss, sexual encounter, or affair may last only minutes or hours, yet its meaning can be enormous because it violates an important relational boundary. Many people regard sexual infidelity as the ultimate betrayal, while others defend it by saying, "It was only sex. It meant nothing." But this defense raises an obvious question: If it meant nothing, why was the relationship worth risking for it?
Change and Familiarity
"The more I see you, the more I want you. Somehow this feeling just grows and grows." —Chris Montez
"Weirdly, I want the unpleasant situation between me and my husband to change. But then again, I would not have an excuse for a hot lover. Just being honest." —A married woman
Emotions typically arise when we perceive significant changes in our own circumstances or in the lives of those close to us. From an evolutionary perspective, attending to change is adaptive because change may signal opportunity or threat. Once we adapt to a new situation, however, its emotional impact often diminishes (Ben-Ze’ev, 2019).
This tendency may appear to work against enduring romantic love. Yet familiarity has its own emotional value. In long-term relationships characterized by commitment and shared activities, familiarity can deepen intimacy and romantic meaning. Change tends to ignite sexual desire, whereas familiarity often nurtures romantic attachment.
Making Love and Having Sex
Although making love usually involves sex, not every sexual encounter can be described as making love. Compared to merely having sex, making love is often more patient, emotionally intimate, and relationally significant. A key difference concerns time. Making love reflects what might be called a patient heart, one that values both present enjoyment and future connection. Simply having sex is more likely to emphasize immediate gratification.
Making love also tends to foster greater intimacy. It involves shared attention, responsiveness, and emotional resonance between partners. In such encounters, giving may become as important as receiving, encouraging a more other-centered form of sexual interaction.
The Intimacy Continuum
"Last night I had sex with my husband, but he did not actually touch me. He just penetrated me. I was so sad I could cry." —A married woman
"I cannot engage in lip-kissing with men I have sex with unless there is profound intimacy. Kissing other body parts, including sexual organs, feels less intimate." —A married woman
The connection between love and sex comes in many forms. Commercial sex illustrates that the two can be separated, while the husband's behavior described above shows that emotional disconnection can occur even within marriage. Love and sex therefore exist on an intimacy continuum rather than as simple opposites.
Sex Essential Reads
Elizabeth Bernstein (2007) coined the term bounded authenticity to describe the sale and purchase of authentic emotional and physical connection in certain forms of sex work. This differs from purely impersonal sexual release. Bernstein notes that some sex workers attempt to create genuine feelings of desire, esteem, and emotional connection, giving clients a sense of being valued and wanted. Accordingly, commercial sex need not always involve what people dismiss as "counterfeit intimacy."
Sexual Afterglow
"While having an affair, I was sexually aroused and began noticing other men noticing me. Even my husband seemed more attracted to me. When it rains, it pours." —A married woman
"My married lover became emotionally distant the moment he ejaculated. The speed with which he withdrew emotionally and physically was astonishing." —A divorcee
Sexual afterglow refers to the positive feelings that linger after a satisfying sexual encounter. Research suggests that these lingering feelings, rather than orgasm alone, play an important role in shaping attitudes toward one's partner. Although less intense than orgasm, afterglow may contribute more to long-term relationship satisfaction. Spouses who experience stronger afterglow report greater marital satisfaction, suggesting that afterglow may help strengthen pair bonds. While orgasm is the clearest expression of sexual intensity, the affectionate interaction that follows sex may do more to deepen a romantic connection. Studies indicate that sexual afterglow lasted at least one day on average and is associated with greater marital satisfaction. The enduring effects of sex, rather than the immediate climax alone, may therefore be especially important for relationship quality and longevity (Breedin, O. W., et al. 2025; Danovich, 2017).
Concluding Thoughts
Love and sex are two central forces in romantic life. Their relationship is complex: sometimes they reinforce one another, and sometimes they pull us in different directions. There is no simple formula for balancing them. Yet relationships are most likely to flourish when sex and love complement rather than compete with each other.
The significance of sex depends less on the physical act itself than on the meaning it acquires within a relationship. Sex may be brief, physically, and seemingly superficial, yet at the same time psychologically and romantically profound. This is precisely why, despite being described as "just sex," it can become one of love's deepest expressions—or one of its deepest betrayals.