Seriously, if we say two men can marry why not allow a man and two women to marry? We have a seriously low birthrate in the developed nations and polygamy would help. We might also bump up the quality of the gene pool a bit if women could marry men who were higher up on the food chain rather than having to settle on bottom feeders.
And never once did the Bible condemn polygamy. In fact only the Koran limits the number of wives a man can have to four.
REASONS to promote monogamous / mutually exclusive sexual commitments:
How about:
* health and preventing disease
* emotional stability and preventing emotional abuse
* prevention of conflicts over finances and property
The Bible forbids fornication and adultery.
So unless multiple partners are mutually husband and wife to one another equally,
then some of the partners can be counted as having relations with someone
other than their spiritual spouse.
Now granted, if someone is going to have multiple partners,
I do believe it is POSSIBLE for, say, two married couples to
marry each other and all have relations with respect to marriage between
spiritual husband and wife.
But sets of three, or other unevenly matched pairs
tend to end in jealousy and disputes and are not recommended.
I don't know if you are just talking hypothetically,
but if you have ever seriously studied triads, swinging, polyamourous
and other multiple relations, you might see the problems caused
when people are not equally and evenly yoked!
Problems are hard enough to resolve with just two people committed
to each other; when conflicts become triangulated with third parties
involved, you risk both emotional harm and also physical conflicts over property.
So no, for emotional reasons alone, I would not recommend
having multiple partners; the most I would recommend is that
married couples team up in sets of four and maybe that would
have added social benefits and stability.
For one man to have several wives or one women to have
several husbands, I think it is more natural to have several partners
but to keep the sex out of it so there is no jealousy or conflicts.
Each person can have one primary partner, but just share
activities or duties nonromantically with the others if that is the purpose.
In some of the polygamous cultures, the purpose of multiple wives
was having a nanny, a cook, a secretary, a housekeeper, so all
that is still possible without getting emotionally entangled in sexual relations.
People by nature get jealous and start making comparisons
so I don't find people can be fair, they underestimate emotional needs.