If there's a theme that should be obvious in these columns, it's that the family is the bedrock of society. And you can't have a healthy family without marriage. Society values marriage not because of abstract values like love and companionship—but because society gets something out of the deal. And even though that sounds harsh, it's true. As National Review points out, society shouldn't be in the business of regulating our emotional relationships. That would just be creepy.
That view of marriage is hard for people to grasp. We want to think of marriage as being about people's feelings. And on an individual level, it should be. But marriage isn't just about the (hopefully) happy couple. The IRS doesn't have a filing category for married couples because the IRS is all about love and romance. Government supports marriage because it creates strong and happy families, which in turn create stronger and happier communities, which in turn creates stronger and happier units of government, which in turn lets government tax everyone until they're no longer happy or strong.
That's why the traditional definition of marriage matters. Because it's part of a much larger societal structure. And that's why messing with it, even if for good reason, can be dangerous. If marriage is the foundation of society, playing around with that foundation can bring the whole house down. That doesn't mean that we can't change marriage with changing times—but we need to ask ourselves if those changes are really for the better.