The bible says a lot of things about a lot of stuff. It tells you how to stay clean, what to eat, how to treat slaves, when it's acceptable to work, kill, or have sex. Among many other things, it's a handbook for daily living in the bronze age. For example,
Thou shalt not lie with mankind, as with womankind: it is an abomination.
--Leviticus 18:22
A couple of centuries ago, people started separating biblical law from the laws that govern us collectively. Communities, families, and individuals can still follow biblical laws all they want, but the rest of us don't have to, and things like slavery or killing, are decided through systems we can all mostly live with, regardless of what bible we read. We did this because couldn't agree on stuff like,
Because of this, God gave them over to shameful lusts. Even their women exchanged natural relations for unnatural ones. In the same way the men also abandoned natural relations with women and were inflamed with lust for one another. Men committed indecent acts with other men, and received in themselves the due penalty for their perversion.
--Romans 1:26-27
We removed the bible from day-to-day law because battles between churches had become an existential threat in the late middle ages. Between all the crusades, inquisitions, and reformations, fields laid fallow, people fought, starved, or succumbed to pestilence, and civilization itself became a shaky proposition. Something had to change. People started looking at how things worked under Greek and Roman democracies, and came up with some new ideas on how to run a society. Some mixture of nostalgia, rationalism, and raw necessity created our modern legal institutions.
Render unto Caesar the things which are Caesar's, and unto God the things that are God's.
--Matthew 22:21
Jesus seemed to know all this was coming. He spoke plainly about how there are matters that are between oneself and God, and then there's the day-to-day like taxes and civic order that are Caesar's problem.
Today homosexuality is viewed largely as a matter to be settled between oneself and God. People might eventually end up in hell, but very few of us believe that anyone should be killed, jailed, or exiled for it here on Earth. Even a few decades ago this wasn't the case. Ask Oscar Wilde or Alan Turing. But when all that is left to discuss are the matters of taxation and civic order, it is also unavoidably Caesar's problem. Children, marriage, and spousal rights are all things that Caesar has to deal with.
For my money, this issue was resolved in Oscar Wilde's day, around the time we instituted civil marriages. Today's marriages are usually done in two parts. First there's the age-old religious part (or the new age part with crystals and bundles of sticks). Second there's the part where the official tells the happy couple that they are married according to the laws of whatever state, territory, province, oblast, prefecture, department, or arrondissement they're in. For things like taxation and civic order, the first part is optional. It's the second part that counts.
It's often overlooked that civil marriage was a common conservative rallying cry in the late 19th century. Catholics saw a threat to the church's authority. Protestants believed that they'd lose control over social norms. And they were right. Today I can have a wild night and get married at Caesar's Palace by Elvis Himself. The next morning I can walk down the street and get divorced just as easily. But I don't want to do that. I don't want to marry a man either. Doesn't mean I shouldn't be allowed to.
Things change. Gay marriage seemed absurd to most people less than a generation ago. God might be eternal and unchanging, but social acceptance of homosexuality, and more importantly same-sex family units, has changed rapidly. And yet, aside from some people's personal misgivings, nobody has been able to demonstrate any harm in two men or women living together, raising kids, sharing resources, or being buried next to one another at the end of it all. The state should not involve itself in people's moral choices, even if it did at certain times in the recent past. Today, few of us would stand for the government having some checklist determining who has the right to marry. Even if we did, none of us could agree on what would be on that list.
In the long term, the argument over who can be married and how was lost when Caesar (and Elvis) got involved. Ever since the enlightenment, Caesar has been the authority we depend on for resolving civic matters. Caesar weighs in on stable households, rights of survivorship, taxation, and visitation. But Caesar has no authority over one's relationship with God, and thus no authority over one's decision of whom to live with, love, and marry.
If gay marriage was in any way disruptive to civic order, then this would all be debateable, but it's not. Churches can marry whomever they choose. Some churches won't marry couples outside of the faith. Some won't marry couples outside of their race. For my part, they should feel free to abide by whatever bronze age rules they find just. But the state cannot.
Marriage has been rendered unto Caesar. All hail Caesar. The gay marriage war is over.
