I admit six days out of seven I feel mighty pessimistic about the prospects for traditional marriage in America and in the West.

It seems likely that “marriage” will become an increasingly flexible institution, both by its legal definition and by our cultural assumptions. The major voices in education, in the media, and in the entertainment industry are so deeply invested in the success of the sexual revolution that it is hard to think the rapid acceptance of gay marriage which we have seen in the last half decade does anything but accelerate in the years ahead. Conservatives and Christians will have all they can handle simply to maintain legal protection and minority rights.

That’s how I feel most days.

But every once in awhile—maybe one day a week, probably on Sundays—I can’t help but hold out hope for traditional marriage. What if “being on the wrong side of history” is more of a progressive ideology than a foregone conclusion? What if our cultural development is not inexorably locked into either a pattern of secularization and sexual liberation? What if the building block of every successful civilization cannot be redefined as easily as some imagine? Are there any reasons to think traditional marriage can make a comeback?

Let me suggest five.

1. Religious fecundity. If demography is destiny, we ought to pay attention to the falling birth rate in this country and in the entire industrialized world. Who is having enough children to replace themselves? It’s not secular people. By definition, it’s not gays and lesbians. It’s religious people—Muslims, Mormons, traditional Catholics, conservative evangelicals. No serious students of these trends can disagree that the more religious and the more traditional a couple, the more likely they are to have a large family. Walk into a church like ours and you’ll find that four kids is normal, five or six isn’t strange, and seven or ten is not unheard of. If, by the grace of God and against all cultural pressures, we pass on the faith and keep our kids in the fold, there is reason to hope that Christian convictions will not go the way of the dodo bird in the next generation.

2. The fickle factor. When you think about how quickly public opinion has swung in favor of gay marriage, it’s clear that the new conclusion has not been reached because of deep, ethical reflection. There was a tipping point—it likely coincided with President Obama’s “evolution”—where opposing gay marriage became a public liability.  Large swaths of the American people are now for gay marriage because it seems too costly—culturally, socially, politically—not to. But what happens when posting that equal sign on Facebook feels so 2013? What happens if the cool crowd gets bored with the new status quo? I suppose many of them will push into darker sexual waters, but what if some push back? What if five years from now we have a Juno-style movie that humorously, and yet provocatively, questions whether our sexual orthodoxies are all they’re cracked up to be? If supporters of marriage don’t cave in, those who swung one way may swing back when it no longer looks like they are “on the wrong side of history.”

3. The results are not in. I remember hearing Os Guinness once remark that sometimes the best cultural argument we can make is simply, “Wait and see.” If God ordered the world to be populated by a husband and wife living in covenant fidelity for the purpose of raising and nurturing their own children, we will see things fall apart when this design is undermined. Every piece of social science research we have already shows that children fare best when raised by a mother and father who are also their biological parents. For the time being, gay marriage doesn’t seem to hurt anyone. And certainly, we should recognize that many kind, loving homosexual partners will raise children in a warm, safe environment. But no one has seen what this looks like on a bigger scale. Very few people dare to talk about the negative health realities of gay sex. Few want to see what even many gay activists admit (and often celebrate), that gay “marriage” is not going to look like June and Ward Cleaver except with two Junes or two Wards. We haven’t had to live with the consequences of gay marriage. If there are no unhappy consequences, then the traditionalists will lose. If the picture doesn’t turn out so rosy, we may see people rethinking their knee-jerk reaction in favor of something never before tested in society at large.

4. Overreach. If the most ardent supporters of gay marriage and the most serious opponents agree on one thing it is that gay marriage is just the beginning of a total transformation of marriage and family as we know it. Does that mean open marriages and multiple marriages and incestuous marriages will eventually be accepted by popular opinion and protected by law? Perhaps. Or perhaps, we will be awakened to the reality that much more is afoot than hospital visitation rights. What will happen when a son marries his elderly father so as to avoid inheritance taxes? Will a majority of the American people say “this isn’t what we signed up for” when there are countless personal stories to share of Christians and other religious persons losing their jobs, their children, and their dignity all because they dare to believe what almost everyone in this country has always believed about marriage? Will the champions of multiculturalism  have the integrity to listen to the Africans and Asians who don’t share our enthusiasm for sexual revolution? Will a generation of twerking daughters convince folks that sexuality without boundaries is morally bankrupt and repulsive? Maybe the frog in the kettle will get too hot too fast and jump for safety.

5. Christian witness. As a Christian, this final point is the most important to me. It’s the one that will most reflect our faithfulness (or unfaithfulness) and likely the point readers of this blog can do the most about. There are more than 300,000 churches in this country. By conservative estimates, there are more than 50 million people that go to church every Sunday. Christians in this country are blessed with a formidable network of Christian schools, colleges, seminaries, parachurch ministries, non-profits, social agencies, publishing houses, magazines, journals, blogs, conferences, and thousands of deep-pocketed donors. As important as the political process is, and the court battles, and the trends in higher education, and the pop culture streaming from New York and L.A., none of it as important as what happens in our churches and in our church supported institutions.

Not just on this issue, of course. There are more important issues than gay marriage. But this issue should matter to us as well. Will we stand fast? We will find a way to be welcoming without affirming? Can we love with unconditional affirmation? Will we have the wisdom to grow in compassion and in courage? Will our evangelical schools and publishing houses compromise? Will our denominations crumble beneath the cultural pressure? Will our academics and pastors lead the way in biblical fidelity and winsome cultural confrontation, or will they let the world press them into its mold? Will we trade the favor of God for the favor of men? If there is no strong voice for traditional marriage, no faithful witness in the world for the beauty of husband and wife as a reflection of Christ and the church, no intelligent defense of all that used to be obvious—if none of this exists in 25 years it will be chiefly our own fault.