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

Monogamy is a social construct borrowed from the Romans, and is a
vestige of the idea that a man owns a woman. Historically most
societies have been poly in some form or other, and as we accept fewer
religious and political restrictions on romantic or sexual
relationships, it makes less and less sense to privilege monogamy.
Jealousy is natural in human relationships, but we are able to deal
with it appropriately in all sorts of contexts. We are simply less
mature in general when it comes to sex. This is not a new observation.
Kohlberg (and later Rest, et al) have looked extensively at moral
reasoning and its development. Moral reasoning can be categorized in
stages, (analogous to Piaget’s stages of reasoning in childhood
development), where people are first able to understand morality in
terms of self-interest, authority, and punishment and later are able
to think in terms of reciprocity, fairness and (hopefully) eventually
higher stages. Consistently, people prefer arguments written at the
highest level they can produce or one level higher. Just as
consistently, people’s moral reasoning when it comes to romantic
relationships lags a bit behind their reasoning in general. Thus it
should not be surprising that people mature enough to handle jealousy
when their best friend hangs out with someone else instead of them are
often not mature enough to handle jealousy when their significant
other finds someone else appealing too. But this is subject to
practice. With practice we learn to deal with our emotions maturely.
When people are able to deal with these emotions maturely, there is no
need for monogamy for most people. We do not have to be controlling of
our partners, forcing them to see only us. We do not have to try to be
our partners’ everything – they can get different emotional needs met
in different social contexts, with multiple people. While of course
this does not work for literally everyone, a lot of people would
benefit from more flexibility than a one-size-fits-all monogamy
permits. This is not just theoretical. Over 40% of marriages end in
divorce, which should be enough in and of itself to abandon the key
legal role marriage plays in society. What’s more, about a third of
those divorces are due to infidelity; presumably even more are due to
other flaws in monogamy such as their preferred partner being good for
them but not enough as a sole partner. Given that so many of these
failed marriages are due to a structural flaw with monogamy, it makes
sense that a whole lot of people currently invested in monogamy would
be doing way better without it. My mind could certainly be changed, we
just need to give polyamory more of a try. Which is happening as we
speak – if it turns out we see way more poly weddings than poly five
year anniversaries, or that kids raised by poly families do worse in
some way, then I would update my beliefs.

2a. A monogamous person is jealous of their partner (for example, because
they’re afraid their partner has a romantic interest in someone else).
In a healthy relationship, what would happen next?

In a healthy monogamous relationship, they’ve agreed about this
beforehand. They’ve surely thought about the possibility that one
might get jealous of the other’s social life, and in a healthy
relationship they communicate before and during. So the jealous one
asks their partner straight up about the extent of the romantic
interest, and gets accurate information. If the answer is “yeah, we’re
just friends”, they can trust that. They can certainly discuss ways to
better deal with it in the future – there has to be a place between
“please don’t tickle your hot bodybuilder friend” and “you can’t have
hot friends” – and they find that compromise. But it’s also possible
the answer is “you are right to be jealous, I do have romantic
feelings”. And ultimately it’s possible that they really should break
up or divorce over those feelings. Even so, honesty is best during
that process.

2b. A polyamorous person has a date scheduled with their primary partner,
but their secondary partner is in the hospital with an emergency and
needs support. In a healthy relationship, what would happen next?

A hospital emergency is important, and takes precedence over a date.
That is true whether it’s a relative, a significant other, or just a
friend. If someone needs your support, you give it. Your primary
partner understands. However, two issues arise. First, cancelling a
date deserves an explanation, while someone in the hospital deserves
privacy if they want it. The answer there, I think, is that your
secondary partner has to understand that you had a date with your
primary partner and that having you come that evening means you will
tell your primary partner that they’re in the hospital if not the
precise details of why. If they aren’t okay with that, they’ll need a
different support person. Second, of course they are going to feel a
little bit miffed at some level that you’ve cancelled their date for
another partner. Intellectually they understand. Subconsciously there
is going to be a bit of emotional labor here, some reassurance.
Emotional labor you may not be in a position to provide after having
just spent the evening performing emotional labor. There should be an
understanding that you’ll debrief a different day.

3. What would happen if 90% of people in a society were polyamorous?
(You may assume they all practice one style of polyamory, or different
styles.)

If 90% of people in a society were polyamorous, polyamory would be the
default. This would impact monogamous people today less than monogamy
being the default impacts poly people. After all, people can always
happen to have only one partner and need not be interested in any
given other person, so there would not be significant stigma
associated with people who have precisely one partner. Whereas today
there is significant stigma associated with polyamory as it’s seen as
reflecting an inability to commit. There might be a bit of stigma
associated with an inability to handle jealousy, but that should be
quite minor. Besides, monogamous people being able to learn to handle
jealousy better should be a benefit for monogamous people under
default polyamory that outweighs the small possibility of a small
stigma. I think some people may be concerned that polyamory would tend
to exacerbate the issue of women dating wealthier men than
themselves/men dating less wealthy women than themselves. That it
would lead to wealthier men having harems while poorer men becoming
incels. I do not think this is likely. After all the studies that look
at this issue appear to suggest that women are in fact okay with
dating less wealthy men while it is men who become insecure when their
female partners make more than themselves. Given this, I think the
problem is invented. In reality, men can and will get over their
social conditioning about being the primary providers.