Friday, September 23, 2011

Utilitarian Argument Against Polygamy

One reason to oppose polygamy is that spouses have a declining marginal utility, and it's best to set up a roughly egalitarian distribution. Your first spouse adds the most happiness to your life, but each additional spouse isn't going to add much more. Better for them to find other people. It's kind of like progressive income taxation, except that you do it pre-emptively instead of occasionally redistributing existing spouses, since that wouldn't work out very well.

7 comments:

Hope said...

Awesome! I had wondered, at one point, what other arguments could be used against polygamy, besides religious ones.

Ben said...

But you are forgetting about the spouses - doesn't the quality of their one choice matter? So why lock out the best choices once one person has got them?

A system that does this only encourages early, inefficient "ground-claiming" - just like the patent system.

jack lecou said...

Did you just inadvertently argue against progressive income taxation for libertarians though? I mean, separating them from their beloved dollars must be every bit as traumatic as redistributing spouses would be. (Worse, maybe. Most people aren't really cut out for mating for life with each other anyway, but I'm not sure I'd say the same about libertarians and cash...)

Jonathan Ichikawa said...

"Better for them to find other people?" I don't get it. We're contemplating a polygamous system; they can find other people AND add some utility to your life.

Neil Sinhababu said...

This is only an argument against polygamous arrangements of a one-to-many sort where the many aren't allowed to find further partners. If they are allowed to find further partners, you're not really taking anyone off the market in a way that makes declining marginal utility issues apply.

Quirk said...

Oh, thanks for clarifying that: you're arguing against star-shaped graphs, not complete, cyclic or otherwise symmetrical graphs. (e.g. Vs instead of triangles.) As an argument against complete graphs it makes no sense, since everyone can be presumed to be deriving equal happiness from the arrangement. Though if you gave an actual function, I suppose you could then work out the optimal size of group (e.g. is everyone in the world married? Is everyone single? Should everyone be in groups of 5? :))

Since you said "polygamy" instead of "polyamory" maybe I should've realized that.

But allowing for people to be different, supposing you have 2 people who each want a relationship with half the energy of that which a 3rd person wants, a V seems like a utilitarian arrangement.

Anonymous said...

Even if diminishing marginal utility begins as early as the second relationship, the decrease in pleasure would be gradual. For example, if a relationship causes 10 points of pleasure, at worst, a second relationship might cause 9 points of pleasure and a third 8 points and so on but 19 is greater than 10 so, *if* the increased benefit is worth any necessary costs, a utilitarian would have to ideally favor polyamory. In a monogamous system, one person gets to enjoy a relationship with another, in a polygamous system, several people get to enjoy a relationship with that person. Monogamy promotes intra-sex competition which discourages egalitarianism. The argument that the second partner won't be as appreciated as much as the first doesn't hold anymore weight than the argument that the first will be jealous if their partner has other partners, especially if the second has other partners for whom he or she is their first.