What Do We Mean by Infidelity, Anymore?

For most of modern history, infidelity has been narrowly defined: sex with someone who is not your spouse. More precisely, genital sex. More precisely still, penetrative sex. This definition made a certain kind of sense when marriage was primarily an economic arrangement, when lineage and inheritance mattered more than emotional fulfillment, and when sex itself was tethered tightly to reproduction.

But we no longer live in that world.

Today, most people do not need a partner to survive financially, to raise children, or to gain social legitimacy. And yet, paradoxically, we ask far more of our intimate relationships than ever before. We want our partners to be lovers, confidants, co-parents, erotic muses, emotional regulators, intellectual companions, and witnesses to our becoming. Against this backdrop, defining infidelity solely by sexual behavior . . . particularly by which body parts touched . . . seems increasingly insufficient.

The question is no longer just “Did you have sex?” The real question is: “What agreements were broken, and what was taken underground?”

From Acts to Agreements

Just as intimacy is multidimensional; emotional, intellectual, spiritual, erotic, experiential, etc., so too is infidelity. Sexual betrayal is only one possible expression of a deeper rupture. Increasingly, my clients report feeling devastated not because their partner had sex, but because something essential was hidden, diverted, or shared elsewhere without consent.

In this sense, infidelity is better understood not as a behavior, but as a violation of relational agreements.

Those agreements may be explicit (“We are monogamous.”) or implicit (“We tell each other the truth.”) They may involve sex, but they may just as easily involve emotional disclosure, time, money, fantasy, or allegiance. What defines infidelity, then, is not the act itself, but the breach of trust created by secrecy, deception, or disavowed desire.

This is why people can feel deeply betrayed by:

• Emotional affairs with no sexual contact

• Ongoing flirtations or erotic texting

• Confiding vulnerabilities to someone outside the relationship while withholding them at home

• Financial secrecy

• Living parallel lives . . . psychological, sexual, or existential . . . that a partner does not know exists

In other words, infidelity often occurs long before anyone touches anyone. It is worth noting that secrecy, omission, and deception are not merely moral or relational events; they are physiological ones. The nervous system registers hidden truth as threat, both in the one who conceals and in the one who later discovers. When honesty feels unsafe, the body adapts by compartmentalizing, numbing, or splitting experience. Infidelity, in this sense, is often preceded by a long period of nervous-system strain, where speaking fully, wanting openly, or risking disappointment no longer feels survivable.

The Cultural Lag

We are living inside what might be called a relational lag: we are attempting to build 21st-century partnerships using outdated maps. Monogamy is still treated as the default moral high ground, yet few couples are given the language, skills, or safety required to renegotiate desire, boredom, longing, or change.

As Esther Perel famously observes, modern marriage asks one person to provide what once came from an entire village; and to do so over decades of psychological development. In this context, affairs often emerge not simply as acts of transgression, but as attempts to reclaim vitality, aliveness, or lost parts of the self.

This does not excuse betrayal. But it does contextualize it.

Context matters because without it, infidelity is reduced to caricature: the villain and the victim, the faithful and the faithless. With context, we can begin to see something more disturbing. but more human; a collision between longing and fear, attachment and autonomy, need and prohibition.

Infidelity Beyond Monogamy

Importantly, expanding our definition of infidelity does not dissolve it. Even in open marriages and polyamorous relationships, betrayal remains possible. In fact, many clients in consensual non-monogamous arrangements report that the deepest wounds come not from sex, but from boundary violations, selective honesty, or unequal power in how agreements are negotiated.

This underscores a crucial point: infidelity is not synonymous with monogamy. It is synonymous with relational incoherence; the gap between what is agreed upon and what is lived.

Whether a relationship is monogamous, open, or polyamorous, betrayal arises when truth is fractured and reality becomes unreliable.

The First Clue: Need

Beneath every infidelity is a need that has become unspeakable.

This is not yet the place to unpack childhood origins or attachment injuries; that will come later in this blog series. But it is important to name that many betrayals begin where desire, loneliness, dependency, or grief cannot be safely spoken within the primary bond. When need is exiled, it does not disappear. It goes elsewhere.

As David Richo reminds us, intimacy rests on presence, honesty, and kindness. When these conditions erode, the relationship may still appear intact on the surface, while something essential has already gone missing underneath.

Affairs, emotional or sexual, are often less about excess desire than about disallowed or disavowed need.

Naming the Terrain Ahead

If we continue to define infidelity narrowly, we miss what is actually happening, and we increase the likelihood that it will remain unaddressed until it explodes. By widening the lens, we can begin to ask better questions:

• What was promised here?

• What became impossible to say?

• What truth about myself felt too dangerous to risk?

• And what was the cost of carrying that alone?

  
  

This series on infidelity will not rush to answers. Instead, it will continue to map the terrain: open relationships and hidden betrayals, gendered patterns and personal histories, deception and self-protection, and eventually, the profound rupture to trust . . . both in the other and in oneself.

Only then can we speak honestly about whether repair is even possible . . . and what it actually requires.

Reflection

Before moving on, pause and reflect without rushing to judgment or explanation:

• When you hear the word infidelity, what images or behaviors immediately arise for you?

• Which forms of intimacy feel most protected in your relationships; and which feel most vulnerable or unspoken?

• What agreements (spoken or assumed) have shaped your sense of safety and trust with a partner?

• Where might secrecy, omission, or self-silencing be present; not necessarily in action, but in thought, fantasy, or longing?

• What needs have felt difficult, risky, or impossible to name within partnership?

Let these questions be informational rather than interrogative. You are not looking for answers yet; only for what becomes visible when the definition of infidelity widens.