He’s Episcopalian, and I really like what he has to say on the subject. To wit:
Many leaders, including our presidents and other politicians, but also religious leaders, local, national and international, have resisted this and been quite vocal about the need to preserve marriage as it has always existed.
When they say this, they demonstrate either incredible ignorance or a wilful duplicity. Three thousand years ago, marriage included polygamy, always one man, many wives. It’s in our Bible. For hundreds of years, until recently, marriage had nothing to do with love or personal relationships and it had everything to do with property and political alliances.
People who tell you that marriage has stayed the same are not telling you the truth. Marriage is always changing. God is always moving—breaking down barriers, including those toward the outcast, the marginalized, the overlooked and forgotten. The world often resists this movement of God.
The church often resists the reality of God as well.
One thing that I don’t know that I agree with him about is the whole “movement of God” thing (because it makes the presumption that God changes, which means that the definition of “good” changes), but I choose to ignore that part.
You may be curious about the polygamy thing (I know I was). Here’s what I could find. So, King David is often described as having multiple wives. I’m not so sure—the translation I’m reading uses language that could be taken several ways; he took many wives, but it isn’t explicit that they were all at the same time. They probably were.
More direct “evidence” is King Solomon, who in 1 Kings 11:3 is described:
He had seven hundred wives, princesses, and three hundred concubines; and his wives turned away his heart.
Now of course, Solomon was directly disobeying Deuteronomy 17:14-17 (which basically says “Kings should not have lots of wives, because the wives will turn his heart away from God.”), and paid the consequences for his actions (1 Kings 11:9-11), so that he had wives is hardly an “endorsement” of polygamy as some would have you believe. But it was indeed recognized as a valid state of marriage.
Deuteronomy 21:15-17 recognizes polygamy as a possible state:
If a man has two wives, the one loved and the other disliked, and they have borne him children, both the loved and the disliked, and if the first-born son is hers that is disliked, then on the day when he assigns his possessions as an inheritance to his sons, he may not treat the son of the loved as the first-born in preference to the son of the disliked, who is the first-born, but he shall acknowledge the first-born, the son of the disliked, by giving him a double portion of all that he has, for he is the first issue of his strength; the right of the first-born is his.
Now, remember, I’m not making the argument (as some like to) that polygamy is endorsed by the Bible. Indeed, the first entrance of polygamy to the Bible is as part of a description of the increasing sinfulness of the world (in the form of Lamech, heir of Cain, who boasts to his two wives of how cruel he is, Genesis 4:17-24). But it would seem that polygamy was, way back when, a relatively common thing.