Cheating is the most scarlet of all flags

Dating a cheater, whether they cheated on you or someone else, is fundamentally about risk management. Whilst people certainly can change, the evidence and logic suggest that reconciling with a cheater deserves far more caution than many offer. It’s a bit like buying a used car that’s already broken down once. Sure, it might run smoothly for a while, but you’ll always be listening for that suspicious rattle. Could it work out? Maybe, by some miracle. But the world is full of stories of those who swore they had changed, only to betray their partner again. 

Building a relationship with a cheater is both difficult and risky. It’s a Sisyphean task, constantly striving towards a seemingly asymptotic goal of trusting someone who has displayed untrustworthiness. The effort required to restore trust is immense, and in most cases, it simply isn’t worth it. Like Sisyphus, you strain against the doubt while fighting an uphill incline. One slip, and you’re back at the bottom of the hill. Some will decry my stance as heartless; That everyone deserves a second chance. My response is that someone who has betrayed the other is not worth taking a risk on, even if it was just a one-off, let alone if it is a case of serial infidelity.

It’s not just a psychological barrier, but a statistical likelihood; a study of more than 400 participants found that those who had cheated are three times more likely to cheat (Knopp et al, 2017). With 45% of those who cheated once doing so again (compared to 18% for those that did not cheat before), it’s almost a coin flip whether they would do it again and blow up the relationship you worked hard to build. Now, one might reasonably point out that 55% did not cheat again. That’s fair. But consider this from a practical angle: if you were offered a chocolate sweet with a 55% chance of being ordinary and a 45% chance of actually being poop, most people would simply buy a different chocolate. It’s important to note that past behaviour is not deterministic of the future; The studies simply indicate that the odds of cheating shift unfavourably for those who have done it before compared to those without a history of infidelity.

To decide to date/reconcile with a cheater, you are implicitly assuming that they won’t repeat the past and betray you. There are only three possible reasons for this:

1) The past cheating was a one-off mistake and they have matured/changed since

2) There were extenuating and idiosyncratic circumstances that no longer apply

3) The cheating was influenced by factors that are now different

The maturation argument has merit in theory. However, growth here means not just feeling remorse but fundamentally altering how one makes decisions under pressure. If someone has cheated before, whether in a past relationship or with you, they have already proven capable of crossing that line. While people can grow and change, the fact remains that they once justified betrayal, deceit, and selfishness to their own moral code and they have been forgiven. That forgiveness itself can even embolden them, making it easier to justify cheating in the future. No matter how charming, kind, or seemingly remorseful they appear, history does have a way of repeating itself. While some will have matured, there is an elevated risk of relapse.

As for extenuating circumstances, I’ve encountered few that genuinely excuse infidelity. I fully support rehabilitation for most criminals; Many steal or commit crimes because they feel they have no choice. Jean Valjean from Les Miserables stole bread to feed his starving family. But cheating? Cheating never stems from necessity. Regardless whether it is a dead bedroom, constant quarrels, or just general dissatisfaction, cheating is never the default. If someone is unhappy in a relationship, they have an ethical and honourable option: they can end it. They can walk away with honesty. Instead, cheaters choose deception, because they selfishly want to cling to the benefits of their original relationship.

As for the idea that “your relationship is different”, if we accept cheating is driven primarily by the cheater, the biggest factor for infidelity is shared within any relationship a cheater in a part of. You may feel a special connection. However, I’d remind you that whoever the cheater cheated on in the past probably felt the exact same thing. It’s a curious human trait to be overconfident. The better-than-average effect is a well-documented phenomenon where most people assume they are smarter than the average person, which is axiomatically impossible. Most of us think we’re the exception to the rule until reality gives us a polite slap. Maybe there are certain traits that separate the current relationship from the past, but you should be aware of the inflated risks you face dating a cheater, as well as the fact that the previous person who was cheated on thought the same.

Beyond that, a relationship is meant to be a place of trust. You shouldn’t have to constantly monitor and second-guess your partner. How do you fully relax around someone who has already proven capable of such betrayal? How do you avoid becoming paranoid or anxious, checking their messages, questioning their whereabouts, and wondering if they’re lying again? A spouse that has strayed could spark crippling doubt in a partner when they stay out just a bit longer than typical, or perceived secretiveness in messaging. This surveillance mindset corrodes the relationship from the inside, even if your partner remains faithful.

Some people fall into the sunk-cost fallacy, thinking that because they have already invested time and love into the relationship, they should keep trying. Unfortunately, it is a logical fallacy for a reason. The past cannot be undone, and dragging yourself through more pain just because you fear “wasting” what you had will only cost you more in the long run. Of course, some circumstances like children or finances may compel a person to stay with the cheater, though it’s important to be cognisant of the risk of the past re-occurring.

This isn’t about being unforgiving or denying people the possibility of change. It’s about acknowledging that you have options. There are billions of people on this planet who haven’t cheated on you that you can settle with instead. Choosing to rebuild with someone who has means accepting diminished trust, ongoing risk, and the emotional labour of constant reassurance. Sometimes that choice makes sense: children in the picture, decades of shared history, and genuine attempts at recovery through transparency and post-nuptial agreements. Most of the time, it simply doesn’t, even though it’s tempting to overestimate the chances.

That assessment is yours alone to make. But make it with clear eyes about what you’re choosing and what it will cost you.

References

1. Knopp, K., Scott, S., Ritchie, L. et al. Once a Cheater, Always a Cheater? Serial Infidelity Across Subsequent Relationships. Arch Sex Behav 46, 2301–2311 (2017). https://doi.org/10.1007/s10508-017-1018-1