Infidelity seems to be coming back into fashion, if it ever went away. I’m not talking about tabloid articles obsessing over the latest outrageous behavior by this or that celebrity. I’m referring to serious authors like psychotherapist Esther Perel, who is of the opinion that infidelity is common, “and yet it is shrouded in secrecy, filled with shame, and often addressed with major judgment. That’s not helpful to the people who are actually experiencing it — or to society as a whole.” Perel’s take is that affairs are the result of a natural yearning for extra-monogamous affairs, and they are thus likely inevitable, if painful.

That sounds all very well and good, but quite a bit of what makes us different from most other species is precisely that we have an ability to reflect on whether something is good or not, and to act on that judgment. A propensity for violence is also natural for Homo sapiens, and yet we don’t condone it among either children or adults, because we think there are better ways to settle disputes. To be sure, we are all imperfect. We will make mistakes and set ourselves back somewhat. But does that mean we shouldn’t even try to do better? The “it’s natural and likely inevitable” defense can too easily turn into a rationalization for a free pass, especially when given the authority of modern science.

I try to practice Stoicism as a philosophy of life, because it is very pragmatic and effective; designed to help us live a life worth living — a eudaimonic existence, as the ancient Greco-Romans would have put it. And the test of a practical philosophy is precisely in how it handles real problems affecting people. So what does Stoicism have to say about infidelity?

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"While open relationships are perfectly permissible, if consensual, a Stoic perspective tells us that infidelity — which involves betrayal — is not. The Stoics believe that a good life is one in which we try to become better human beings."

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The first stops, of course, are the ancient authors themselves. But in this particular case they turn out not to be too helpful. The Stoics did write about sex and relationships, but they were split in a dramatic fashion on this subject. The late Stoics of the Roman Imperial period, like Seneca and Marcus Aurelius, were rather conservative, by modern standards. Look at what Seneca writes to his mother, from his exile in Corsica, where he had been confined by the Emperor Claudius:

“If you consider sexual passion to have been bestowed on mankind not for the sake of pleasure, but for the continuance of the race, all other desires will pass harmlessly by one who is safe even from this secret plague, implanted in our very bosoms.” (To my Mother Helvia, on Consolation, XIII)”

The typical view of the Roman Stoics was that sex is for procreation, and it should be done only within marriage. But that’s more a reflection of Imperial Roman prudishness rather than of Stoic philosophy. How do I know? Compare the excerpt above with this passage from Diogenes Laertius, who tells us how Zeno of Citium, the founder of Stoicism, saw things just a few centuries before Seneca (while living in the much more licentious Athens, not in Rome):

“In the Republic [Zeno] lays down community of wives [i.e., free love] … he bids men and women wear the same dress and keep no part of the body entirely covered.” (Lives of the Eminent Philosophers VII.33)

I could pick and choose arbitrarily between Zeno and Seneca, but that would be cheating. Instead, I will take a broader perspective and see what we can derive from Stoic philosophy’s principles, sidestepping the cultural biases of individual authors.

The answer, I think, is pretty clear: while open relationships are perfectly permissible, if consensual, a Stoic perspective tells us that infidelity — which involves betrayal — is not. The Stoics believe that a good life is one in which we try to become better human beings by practicing four cardinal virtues: practical wisdom (the ability to successfully navigate tricky situations), courage (to do the right thing), justice (in this instance, behaving in the right way toward others), and temperance (exercising self-control and restraint).

We have plenty of chances to practice all four virtues pretty much every day. How do I balance my career and family life? (Practical wisdom). Should I stand up for my coworker when my boss becomes abusive? (Courage). Should I tip the waiter generously rather than saving a few bucks by shortchanging him? (Justice). Should I order the double cheeseburger with fries or opt instead for a healthy quinoa salad? (Temperance).

At least three of the virtues are obviously at play when we consider embarking in an affair that has not been sanctioned within our relationship. (By contrast, if our partner has agreed that having sex with other people is okay, and especially if that arrangement is reciprocal, than I see no ethical qualms, from a Stoic point of view; indeed, that would result in a situation similar to the one imagined by Zeno for his ideal society.) The first one is, obviously, justice: I’m pretty sure you would feel hurt and resentful if you found out that your partner had been cheating on you. So it would be unjust to inflict the same on him or her. Second, courage: to firmly (and politely) decline the alluring advances of a potential sexual partner, if the occasion to cheat is presented to you. Lastly, temperance: the self-control of not acting on what Perel rightly calls a natural desire, for the simple reason that it is not healthy for your soul. (I use the term “soul” in a generic sense, not in the mystical-religious one. The Stoics were materialists and thought that our souls are made of stuff. They are the part of the brain that is in charge of our decision making.)

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"Psychologists are right in pointing out that we do desire things that are not good for us, and also in noting that we slip more often than we’d like. But a slip it is nonetheless, one that causes pain to people we love"

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Here is how Epictetus, the slave-turned-teacher, colorfully puts the broader point: “Provoked by the sight of a handsome man or a beautiful woman, you will discover within you the contrary power of self-restraint. Faced with pain, you will discover the power of endurance. If you are insulted, you will discover patience. In time, you will grow to be confident that there is not a single impression [i.e., initial judgment] that you will not have the moral means to tolerate.” (Enchiridion 10)

That broader point is that we have more moral fiber than we might realize, and that, in fact, the more we exercise it, the stronger it gets. Like going to ethical gym, if you will. Of course, psychologists are right in pointing out that we do desire things that are not good for us, and also in noting that we slip more often than we’d like. But a slip it is nonetheless, one that causes pain to people we love, and that we will soon regret precisely because of the harm it causes (and perhaps also because of the legal bills that accumulate after our spouse files for divorce…).

It is the same in other, perhaps more mundane, areas of our life. Take eating, for instance, something that is just as natural as sex, and even more fundamental. Musonius Rufus, Epictetus’ teacher, thought that we have three perfect chances to exercise the virtue of temperance, one for each meal of the day:

“Mastering one’s appetites for food and drink is the beginning of and basis for self-control.” (Lectures 18a.1)

In the case of our diet too, we want to do better, and we know what is best for us, and yet we fall into temptations, eat and drink too much, and not always stuff that is good for us in the first place. Now imagine if your doctor took the same approach as we have seen above from Perel: “It’s okay, don’t worry about it, the worst thing that can happen to you is diabetes, or a heart attack!” Would you go back to that doctor and trust him with your health? I sincerely hope not!

It is the same with philosophy. In fact, the ancient Stoics (as well as several other Greco-Roman philosophers, including the Epicureans) explicitly drew a parallel between medicine and philosophy. The first one takes care of your body, the latter of your soul:

“And yet I [as a philosopher] won’t have done you any harm – any more than a mirror is to blame when it shows a plain person what they look like; or a doctor is mean if he tells a patient, ‘Look, you may think this is insignificant, but you’re really sick; no food for you today, only water.’ No one thinks, ‘How rude!’ But say to someone, ‘Your desires are unhealthy, your powers of aversion [i.e., to avoid things that are not good for you] are weak, your plans are incoherent, your impulses are at odds with nature and your system of values is false and confused,’ – and off they go alleging slander.” (Epictetus, Discourses II, 14.21-22)

So it’s up to you. Do you want to be sick in body and mind? Then by all means, eat junk food and indulge in infidelity. Is your goal to be a better, healthier person? Stick to the quinoa salad and work on your relationship. I’m going to bet you will not regret the latter course of action, in the long run.

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Image Credit: Celia Johnson and David Howard in David Lean's Brief Encounter (Criterion, 1942)