1. Why do you believe what you believe? What would change your mind?

Vicarious enjoyment of your partner’s happiness and well-being is a major component of romantic attraction. When they get an unexpected bonus at work, succeed at a difficult project, or tell you how much fun it was to reconnect with their old friend, you’re happy for them, which makes those events good for you even when they don’t affect you directly. In a relationship, there are many opportunities to make a partner better or worse off, and because you care about them, the latter should give you significant pause.

One way you can make them worse off is by preventing them from engaging in something good for them. For example, if your partner loves home improvement and wants to remodel the basement, but you hate the sounds of drilling, hammering, and sawing, you could unilaterally impose that preference, claiming a right to live in peace and quiet, and maybe they’d agree, disappointed. That’s a solution that many people will intuitively reach for, but it’s unsatisfying if you think about it – you care about them and want them to be able to do stuff they like. Instead, think about their experience of liking it and focus on it, then compare that to how much the noise would bother you. This won’t necessarily change your mind, but you may find that your considered preference is less restrictive.

What does all of this have to do with polyamory? The same principles apply.

Monogamy is a total restriction on having other partners for the duration of the relationship. Being a restriction, it should give us pause as we scrutinize it – do I really want to make my partner worse off by removing their option of having multiple simultaneous relationships? If being with someone else at the same time would be good for them, that’d be a significant positive for me because I care about them. So I have a strong reason to let them do what’s good for themselves here.

But, as in the home improvement case, this reason isn’t necessarily decisive – maybe the costs of polyamory outweigh this benefit. What kinds of costs does polyamory have?

You might feel that it’s disrespectful for your partner to have or seek out other partners, to the point of it being a betrayal. Since we live in a predominantly monogamous culture, the concept of romantic partnership has become associated with strong forms of exclusivity. But whether it’s actually disrespectful within a particular relationship depends on whether it’s monogamous. Not everyone follows the same norms about how to express respect. For example, some couples address each other in ways that on the surface seem rude and insulting, but they mean and understand it affectionately; but if another couple used that language it would be interpreted as hostile. Similarly, if you honestly express that you’d be fine with your partner dating others, it wouldn’t be disrespectful for them to do so. It’s bad in a monogamous relationship because it involves violating a serious agreement, but the absence of that agreement is part of the premise of polyamory.

You might be worried that dating others gives your partner more opportunities to leave you. It does, but on the other hand, they have less reason to leave. When you’re monogamous, all possible romantic relationships are in a high-stakes competition against each other, and if your partner wants to pursue another opportunity, they’ll break up with you. But in polyamory, you can continue the relationship as long as you both deem it worthwhile and good in its own right. There are still trade-offs in allocating time and energy to relationships (just like relationships in general compete with work and hobbies), but the stakes are much lower.

More importantly, while you hope your partner won’t want to end your relationship, you also don’t want them to stay if leaving would be better for them. If you prevent them from making friends, or keep them locked up in your basement, they’ll definitely have to stay, but that’s very much contrary to caring about what’s good for them.

You might be envious that your partner is getting more attention from others than you are. To feel this way is a genuine character flaw. If you care about your partner, it’s good when things go well for them, so it’s just as wrong to be envious of their romantic success as it is of their successes in their career or hobbies. It’s fine to want more people to be interested in you, but you shouldn’t feel better about it if your partner’s romantic life gets worse. A romantic relationship should be the ultimate harmony of interests, and this is the opposite of that.

A different kind of cost is that polyamory might seem incompatible with your preferences or circumstances. For example, you might want a lot of attention from your partner, or you might have a young child who’s occupying much of your energy and you want to make sure you make time for each other. Initially, these might seem like reasons to be monogamous, but monogamy is more than that – it’s a restriction on having other partners at all, at any point in the relationship. So as long as you’re getting enough attention, that’s not a reason to object to your partner having brief flings; or you might resume having other partners more seriously once the child is older and more independent.

Similarly, polyamory is perfectly compatible with getting married and having children, not liking orgies, and even with not being interested in having multiple partners yourself. All that it requires is being okay with your partner having other romantic partners.

While the most important benefit of polyamory is freeing your partner to pursue their good, it has other upsides as well. To list a few examples, it’s an opportunity to learn from multiple relationships at the same time – if you learn something (e.g. communication techniques, ways of addressing some problem) through interaction with one partner, the others benefit as well. It enables greater openness within a couple – monogamous culture tends to discourage the discussion of attraction to others and anything related to it. And it’s a good way to make friends – since your partner is interested in you, they’re probably interested in people similar to you, and will want to have them around.

There are probably some people with a deep-seated fundamental preference against their partner having other partners. They should actually be monogamous. But I doubt that’s as common as it seems. Monogamy is very much the norm and most people don’t seriously consider violating social norms even when it’d be good for them. In a world where something as trivial as “talk to your partner” is actually useful problem-solving advice, how people actually conduct their romantic relationships is often far from optimal.

I understand if all of this sounds pushy or preachy. To some degree, that’s inevitable for any view that questions common personal practices. But in all of this, I’m ultimately appealing to your self-interest. Your relationship isn’t some altruistic self-sacrifice, but a joint venture for mutual benefit – you like your partner and are made happier by their happiness. If there’s a good opportunity to benefit yourself via this channel, wouldn’t you want to know about it? Just speaking personally, I would feel foolish if an excessive adherence to social norms made me refuse this kind of $100 on the sidewalk.

I’m not sure what would change my mind. If fundamentally monogamous people are the vast majority, there’s less to be gained from making polyamory socially acceptable, but on an individual level it’s still worth considering – just like it’s worth considering whether you’re bisexual even though most people are straight. The costs of thinking about it are low, and the benefits potentially high.

It’s certainly possible that if polyamory became widespread, some people would practice it poorly, and find new ways to make themselves and their partners miserable, so it could be bad for society in that sense. But I think that’s the wrong standard. You can misuse a good tool in a way that makes you worse off, but even if the misuse is common, the right moral is not “the tool is bad”, but “don’t be a misuser”. The frequency of bad relationships doesn’t make me condemn romance, so I wouldn’t condemn polyamory for the misbehavior of some of its practitioners.

2. A polyamorous person hates their partner’s other partner (their metamour). In a healthy relationship, what would happen next?

It depends on the closeness and commitment level of your relationship, and how seriously you hate your metamour. If you genuinely think they’re a bad person, the appropriate response is different from something lighter, like if their mannerisms just annoy you. If you think they’re fine and just don’t like being around them, you can probably talk to your partner and arrange to never be in the same room, which would solve most or all of your problem.

If you hate your metamour for serious reasons, you should talk about it with your partner, probably asking them to keep what you say in confidence. Maybe your partner will show that you’re wrong to hate them – you might misunderstand your metamour, maybe you’ve heard something bad about them that’s actually not true, etc. Or you might persuade your partner and they’ll decide to break up with your metamour. If you don’t know your partner that well (maybe you’ve only recently started dating), this is a good opportunity to learn more about them, and maybe you’ll learn that they like your metamour because they’re bad too, in which case you’ll probably want to break up.

The hardest case – fortunately, the least likely – is if your primary partner is also in a close and highly-committed relationship with a seriously bad metamour, neither of you can change the other’s mind, but you still want to stay together. In that case, you should think about how much the metamour can harm you directly, and distance yourself from them as much as you can. Throughout that process, be sure to explain to your partner what you’re doing and why, so you don’t look crazy and your motivations aren’t mistaken for envy. Then be supportive of your partner and watch for anything bad happening in their relationship – but don’t be overbearing, so they’ll be open with you and tell you if anything happens.

3. What would happen if 90% of people in a society were polyamorous?

Currently, there are many people who are terrible at relationships. Between abuse, lack of communication, dragging on the relationship despite great incompatibility, etc, they make miserable what could be wonderful. We disallow children from having relationships because they’re incapable of reliably reasoning about their interests and/or are emotionally immature. Adults are generally rightly independent and their associations are up to them, and I’m not questioning their right to choose, but when it comes to relationships, otherwise competent adults sometimes act little better than children. I don’t expect polyamory to change that. Where now a dysfunctional couple mutually abuses each other, they’d get to share that with more unlucky partners, and receive it from them in return. Some say that normal people can’t handle polyamory – I say they can’t handle monogamy either.

A mostly polyamorous society would have some marginal improvements over the current one. Sexual and romantic envy would likely be less socially acceptable. People wouldn’t be able to tell their significant other that they can’t spend one-on-one time with friends of the opposite gender, as some do now. There would no longer be the expectation that extramarital relationships are betrayals that should lead to divorce. And one of the worst media tropes, “I saw you with a member of the opposite sex doing something innocent that I misinterpreted as sexual and now I’m mad at you and won’t talk”, would be banished from this earth.

But unreasonable people would just be mad at their partners about something else. Many relationships currently suffer from romance being treated as a reason-free zone, and if that changed, I expect polyamory would be more common, but merely swapping it in for monogamy wouldn’t solve the root of the problem.

As for problems like STDs or unwanted pregnancies, I think they’d be less of an issue that one might expect. We already have norms about safe sex within hookup culture, and that could easily be extended to relationships. Still, some impulsive people would continue to suffer the consequences of their decisions, and each additional partner would be another opportunity for things to go wrong for them. But while this might lead some to write “Polyamory has been a disaster for [insert group here]”, the right conclusion would be “[insert group here] has been a disaster for themselves”.