The strongest love will naturally usually be in monogamous relationships except in the unusual case that you, X, and Y are all mutually in love.
There may be some biological basis for jealousy; I would be surprised if it weren't adaptive. However, most people make a constant effort to suppress behaviour that would be (technically) adaptive, or to engage in behaviour that is clearly maladaptive (like, say, not having children so they can have a career). While there may be some biological reason for jealousy, that does not explain or justify its general social endorsement.
More specifically, the concept of love seems to have the concepts of fidelity and jealousy inextricably woven into it, at least in mainstream Western culture. On a philosophical level, this doesn't exactly make sense. If we care about the overall happiness and flourishing of man kind, it seems likely we would be far better off if we took the effort we put into suppressing, say, premarital sex, and moved it into suppressing jealousy.
Obviously, this is the view of a rather small minority, but it is nonetheless fascinating that most people are incapable of conceiving of love without fidelity: consider the seriousness of the implications of a romantic partner saying, "I love you," for most people.
If we care about the overall happiness and flourishing of man kind
That's a pretty big "if", there. I think the percentage of people who genuinely care about that is vanishingly small. How many Americans do you think would agree to erase the US entirely if they were absolutely certain that it would guarantee the happiness and flourishing of the rest of the human race? Do you think you could find even ten thousand?
Many of us are familiar with Donald Rumsfeld's famous (and surprisingly useful) taxonomy of knowledge:
But this taxonomy (as originally described) omits an important fourth category: unknown knowns, the things we don't know that we know. This category encompasses the knowledge of many of our own personal beliefs, what I call unquestioned defaults. For example, most modern Americans possess the unquestioned default belief that they have some moral responsibility for their own freely-chosen actions. In the twelfth century, most Europeans possessed the unquestioned default belief that the Christian god existed. And so on. These unknown knowns are largely the products of a particular culture; they require homogeneity of belief to remain unknown.
By definition, we are each completely ignorant of our own unknown knowns. So even when our culture gives us a fairly accurate map of the territory, we'll never notice the Mercator projection's effect. Unless it's pointed out to us or we find contradictory evidence, that is. A single observation can be all it takes, if you're paying attention and asking questions. The answers might not change your mind, but you'll still come out of the process with more knowledge than you went in with.
When I was eighteen I went on a date with a girl I'll call Emma, who conscientiously informed me that she already had two boyfriends: she was, she said, polyamorous. I had previously had some vague awareness that there had been a free love movement in the sixties that encouraged "alternative lifestyles", but that awareness was not a sufficient motivation for me to challenge my default belief that romantic relationships could only be conducted one at a time. Acknowledging default settings is not easy.
The chance to date a pretty girl, though, can be sufficient motivation for a great many things (as is also the case with pretty boys). It was certainly a good enough reason to ask myself, "Self, what's so great about this monogamy thing?"
I couldn't come up with any particularly compelling answers, so I called Emma up and we planned a second date.
Since that fateful day, I've been involved in both polyamorous and monogamous relationships, and I've become quite confident that I am happier, more fulfilled, and a better romantic partner when I am polyamorous. This holds even when I'm dating only one person; polyamorous relationships have a kind of freedom to them that is impossible to obtain any other way, as well as a set of similarly unique responsibilities.
In this discussion I am targeting monogamy because its discovery has had an effect on my life that is orders of magnitude greater than that of any other previously-unknown known. Others I've spoken with have had similar experiences. If you haven't had it before, you now have the same opportunity that I lucked into several years ago, if you choose to exploit it.
This, then, is your exercise: spend five minutes thinking about why your choice of monogamy is preferable to all of the other inhabitants of relationship-style-space, for you. Other options that have been explored and documented include:
These types of polyamory cover many of the available options, but there are others; some are as yet unknown. Some relationship styles are better than others, subject to your ethics, history, and personality. I suspect that monogamy is genuinely the best option for many people, perhaps even most. But it's impossible for you to know that until you know that you have a choice.
If you have a particularly compelling argument for or against a particular relationship style, please share it. But if romantic jealousy is your deciding factor in favor of monogamy, you may want to hold off on forming a belief that will be hard to change; my next post will be about techniques for managing and reducing romantic jealousy.