Thank you for your rational replies. You make good points, and I don't want to get caught up in the semantics.
"'Marriage laws' on the books since Ancient History" imply laws that are divorced from religion. I agree that there's a legalistic "marriage" in addition to the religious one. And in history, there have been "perverted" versions of "marriage" allowed, haven't there? Many of your "legal" marriages have included polygamy.
I'm suggesting that if we choose to have the government involved in bonds between people, for whatever reason, we shouldn't pervert "marriage" to do it.
“’Marriage laws’ on the books since Ancient History” imply laws that are divorced from religion.
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Actually, the opposite is true. In ancient civilizations laws were given by God (or the gods) and a means of enforcement of His (or their) laws. Alan Deshowitz (as much as I hate him) argued that the Decalogue was the first written legal code, which while not exactly correct, does give a good example of laws coming from the Divine.
Western Civilization from the time of the Greeks have abhorred polygamy. In modern history, the Republican party was founded to combat the ‘twin relics’ of barbarism - slavery and polygamy. The Mormon church (and later breakoffs) are the ones that have argued that religious or spiritual marriage can and should be divorced from the legal entity of marriage.