Constitutional amendments aside, here is how best to preserve the sanctity of marriage.

-- Insofar as "sanctity" means to be held sacred or holy, the major faiths must resume treating marriage as if it were, well, important. This means that getting married must again require some amount of effort on behalf of those who are getting married: going through the various rituals and/or training that used to be required in some churches/religions, paying dowries, and so on. And, of course, honoring the tradition of having marriages pre-arranged by a morally upright, disinterested third-party whose job it is to bring together two people who have never met before. Hey, it worked for our great great grandparents, right?

-- It also means that getting out of a marriage must be, well, difficult. To make divorce an exception rather than a rule, make the cost of divorce high. Excommunication from the church used to be a big deal. But civil penalties can be imposed, as well. You need very special legal grounds, argued in a court of law. No quickies. Divorcees lose certain legal privileges, like the right to vote or otherwise take part in government, since we wouldn't want people who violate a sacred trust to be in any way entrusted with the affairs of state. Oh, and divorce would be heavily taxed.

-- The penalties for violating the oaths of marriage would also have to be severe. Infidelity by either partner? Stoning. To death. I'd also suggest similarly harsh penalties for spousal abuse, even though there's not much of a tradition of punishing spousal abuse.

Ah, but if we want sanctity for marriage, we need more than to make it costly to get into and out of. We also need to provide some holy benefit. Some religions, like the Mormons, allow women into heaven if they get married (as part of a family deal -- if the husband ain't going, neither is the wife). But what incentive is there for the men? Can someone familiar with the world's major religions help me out here? What are the blessings accorded to married people that makes marriage better than singlehood (or non-married couplehood, or non-married polygamy, etc., etc.)? Once I know that, then perhaps I can make suggestions for changes to our civil policies to incentivize marriage, as well.

But, in the meantime, let's bring back arranged marriages and stoning for breaking the vows. That should go a long way toward restoring the former glory of marriage.