This is the question that won’t leave you alone.
Not the practical questions — what happens now, who knows, what do we tell the kids. Those are urgent, but they’re manageable. This one is different. This one sits underneath everything else and keeps surfacing.
“Why?”
You want an answer that makes sense. Something that explains it in a way that gives you solid ground to stand on. And the first answers that come — they chose someone else, they were selfish, they didn’t value what we had — feel true but don’t quite satisfy. Because they don’t actually explain how. How the person you know, the person you built a life with, got there.
Here’s what I’ve found, sitting with couples who are trying to answer this question together.
The obvious answers aren’t wrong — they’re just incomplete
Yes, affairs involve a choice. Yes, there are people who cheat carelessly, repeatedly, without real remorse. Yes, some people have affairs simply because the opportunity was there and their commitment wasn’t strong enough to hold.
I’m not going to pretend otherwise, and I won’t dress this up.
But in my experience, those cases — where the explanation really is that simple — are rarer than you’d think. For most couples who end up in front of me after an affair, the honest answer is more complicated. And that complexity, uncomfortable as it is, is usually what leads somewhere.
The question isn’t instead of accountability. It sits alongside it. Understanding why something happened doesn’t excuse it. But it does make repair possible.
What tends to emerge when you look underneath
I use Internal Family Systems therapy — IFS — as my primary lens when working with couples after an affair. One of the things IFS makes visible is that most of our behaviour, including behaviour that causes real damage, comes from parts of us that are trying to meet a need. Often a need that has been unmet for a long time.
That doesn’t make it okay. But it does make it understandable. And understandable is where the real work begins.
Here are some of the things that actually emerge in the room. Not as excuses. As territory.
A part that felt invisible.
Not unloved, necessarily. Not uncared for. But unseen. Something in them that wasn’t being reached — their humour, their ambition, their sexuality, their fear, their need for adventure or stillness or being known in a particular way. The affair didn’t create that need. It found it, and fed it.
This is one of the most painful things for a betrayed partner to hear — that their person was feeling invisible while standing right next to them. But it’s also one of the most important. Because it opens a question the relationship hadn’t found a way to ask.
A part that had stopped believing things could change.
Many affairs happen not at the beginning of disconnection, but after a long period of it. Attempts to raise things that went nowhere. Conversations that turned into arguments. A slow accumulation of moments where one person stopped trying to reach the other because it hadn’t worked.
The affair, in this context, isn’t a sudden rupture. It’s the visible end point of something that had been happening quietly for years. That doesn’t shift responsibility. But it does change the map of what repair needs to address.
A part carrying something that had nothing to do with you.
Sometimes — not always, but sometimes — what drives an affair isn’t primarily about the relationship at all. It’s about something unresolved in the person who had it. Old wounds around worthiness, approval, or being desired. A part that learned early that love is conditional, or scarce, or always about to disappear — and that keeps seeking reassurance in ways that don’t actually satisfy the original hunger.
This is perhaps the hardest version to sit with, because it’s the one where you could have done almost everything differently and it might still have happened. That’s not a comfortable truth. But it’s sometimes the honest one.
A part that was afraid of the conversation.
Affairs sometimes happen because the thing that needed to be said in the relationship never got said. Not because the person was cruel or cowardly, but because the stakes felt too high — saying I’m not happy, I need something different, I’ve been feeling alone carries the risk of breaking something. The affair becomes a way of having a need met while avoiding the conversation that might have met it directly — and honestly.
What this means for the betrayed partner
Reading this, you might be asking: does any of this mean it’s my fault?
No. Full stop.
The choice to have an affair — and it is a choice — belongs entirely to the person who made it. There is no version of being a flawed partner, a distracted partner, an emotionally unavailable partner, that makes an affair the appropriate response. The appropriate response is a conversation. Or a decision to leave. Not this.
What understanding the why does — for both of you — is give you something to actually work with. If you decide to stay, you’re not just trying to rebuild trust in the abstract. You’re looking at what was actually happening, naming it, and figuring out whether you can build something different from it.
That’s a different kind of repair. It’s harder and slower than pretending it didn’t happen. But it’s the kind that tends to hold.
The question underneath the question
What I find, after sitting with couples through this particular fire, is that why rarely has one answer. It’s usually a few things sitting on top of each other — some about the person who had the affair, some about the relationship, some about circumstances and timing and the specific way two people’s histories collided.
The couples who manage to hold that complexity — who can say this was wrong, and I want to understand it, not just judge it — are the ones who tend to find something real on the other side.
That’s not easy. It’s probably the hardest thing I ask couples to do.
But it’s the work that actually leads somewhere.
If you’re trying to understand what happened
The why is not something you can usually get to alone, or quickly, or in the charged atmosphere of the first weeks after discovery. It needs space, careful holding, and someone who can sit with both of you without taking sides or rushing you toward a conclusion.
It also needs time — not the fifty minutes a week that gets lost between sessions, but sustained, concentrated work where you can actually stay in it long enough to reach something real.
That’s what the intensive format is built for. Not to give you the answer. But to give you the conditions where you might actually find it together.
If you’re trying to make sense of what happened — and work out whether repair is possible — I offer a private 2–3 day Couples Crisis Intensive in Zurich. Find out how it works →
— Alister Gates is an IFS-trained therapist and couples counsellor based in Zurich, working with individuals and couples online across Europe, the US, Australia and New Zealand.