Modern infidelity is different than traditional infidelity and sits on top of the romantic ideal that you find "the one" and that if you have everything that you need at home, you have no reason to go looking elsewhere. And if you have an affair, it's a symptom of a flawed relationship. If you don't apply the deficiency model to the relationship, then you apply it to the person. The person who strays is selfish, immature, addicted suffers from insecure attachment. And the person who doesn't stray is the committed partner: mature, stable, and non-selfish.

I believe that the vast majority of people that are unfaithful are monogamous in their beliefs. The ones who are not monogamous in their beliefs either live in poly relationships or consensual non-monogamous relationships, or they have divorced. If it's very bad, then people don't stay married these days in the West. They can be married and have their family, but they want something else - they want something that they don't have in their lives, or simply to be someone that isn't who they are in the context of their marriage.

We know desire is rooted in absence and yearning. What you don't have is often ten times richer than what you actually experience. An affair is a perfect erotic plot because it fits the erotic equation of psychotherapist Jack Morin: "Attraction plus obstacle equals excitement.".

A peer relationship is one where the partners experience an affectionate, companionate coupledom. They are friends. They are the product of the egalitarian model; they are good life partners, but are often less sexual.

The vast majority of unfaithful people are experiencing a conflict between their values and their behavior, and that is the mess of infidelity. It's not an either-or. The idea that you would ask, "How can you say you love your husband and you want to stay married, and you also are having an affair?" Because we are not the same woman, or the same man. Because sexual revolutions don't take place at home. Because for most of us, freedom wasn't something that we experienced in our family, but usually outside of our family.

Secrecy fuels erotic intensity because it makes you feel like you're doing something that is entirely yours. It gives you the sense of autonomy, the sense of freedom, and the sense of sovereignty. And then you add to that the sexual energy. In many affairs, people will tell you they slept with the person three or four times, but the story went on for months. That's an important thing because many people who have affairs often have very good sexual relationships at home. It's not necessarily a compensation story. But affairs offer a different sexuality with a different context.

Even a good marriage leaves people with longings for certain things their marriage will never be. So, do they accept that, make compromises, and say, "You can't have everything in life," which is what we always did? Or do they say, "I deserve more. I want to experience that thing and, you know, I have fifty more years to live than I used to." It's not necessarily that we have more desires today, but we do feel more entitled to pursue them. We live in this "right to happiness" culture, and yes, we do live half a century longer than we used to.