Mostly we see "polygamy" as meaning "man is in charge, and can take as many wives as he wants". This is unfair on any wives who aren't willing to share him. And when we hear the word "bigamy", we usually think about a man from a monogamist section of society who has two families, each secret from the other. Both women are then shocked when the man is taken to hospital and they are both called to his bedside. This is obviously not OK.

But if a polygamist family wants legal recognition for an arrangement where additional adults can join the marriage with the consent of all those who are already in it, I don't see why they shouldn't have that recognition. We should only ban things that are harmful.

However, when it comes to the civil consequences of marriage, such as social security benefits and inheritance rights, the legislature would have to be careful not to give unfair advantages to polygamists. To take a simple example, if a state's inheritance law says that the spouse of someone who dies intestate inherits a maximum of $300,000 from the estate, with the remainder going to the deceased's children, that $300,000 should be split equally between all the surviving spouses in a polygamist family. They shouldn't get $300,000 each, as that would unfairly disadvantage the children.

Any state pension payable to widow(er)s should also be split. Over time this will even out, since after spouses 1 and 2 are both dead, spouse 3 will get a widow(er)'s pension (or a fraction of one) in respect of both. And so on. I realise it would get very complicated in some circumstances, but I'm sure the civil servants could work it out.