The contrast could hardly have been starker.

As the Senate debated the Federal Marriage Amendment defining marriage as between one man and one woman, voices in the media and on the Senate floor rose to complain about what a waste of time it was. So many issues seem so much more pressing, they said: Iraq, global warming, AIDS.

At the same time, the Vatican was releasing a document about the fundamental importance of the family.

“Never before has the natural institution of marriage and the family been the victim of such violent attacks,” said the document. “The family and marital life models are changing … [and] if we look at the lengths people go to avoid having children, including contraception as well as abortion, the eclipse of any reference to God looks clear in the predominant view of responsible procreation.”

So, which is true? Is marriage a side issue distracting us from the real problems of the day? Or is it fundamental?

We take the Vatican’s side, of course. But it’s important to see why.

“Man is a family being,” says the new document, “and as such he is a social, political, economic, cultural, legal and religious being. The family, which touches on all of these essential aspects, needs services, help, protection and endless promotion.”

The family, quite simply, is the fundamental building block of all of those other spheres in life.

When a mother and a father love each other and their children, their children will, by and large, love them back. This will provide them the model they need in order to respect authority in the political and legal orders, and it will give them the incentive they need to be good, productive citizens.

Statistics bear this out. A father and a mother together providing for the needs of the family are much less likely to fall below the poverty level than single mothers and their children. Abandonment by the father is the leading cause of poverty.

 Where a strong family unit doesn’t exist, the positive “by-products” of strong families aren’t likely to exist, either. In communities where there are large percentages of children born out of wedlock, there is widespread poverty, more unemployment, more crime, more violence.

Society has always severely restricted marriage. It isn’t a merely a package of benefits available to roommates, relatives, best friends or lovers. It is society’s way of protecting a unique relationship between a man and a woman: the kind that is life giving, permanent and exclusive. Society protects this relationship because it is essential to our future that children be brought into the world in stable, loving environments.

To reduce marriage to an insurance-sharing living arrangement of same-sex lovers is to defeat the very purpose of marriage.

People fall in love and become lovers all the time. The state has no interest in recognizing their love, and they should have no reason to crave the state’s recognition of it.

The state’s interest in marriage isn’t to ratify feelings of human love, but to establish a firm commitment from a husband and wife that they will enter the kind of relationship that lasts, is exclusive and is geared toward producing children.

The laws of a land don’t just restrict people; they teach people. Thus traffic laws don’t just warn us about tickets — it teaches us that we are expected to drive responsibly. In the same way, a strict marriage law doesn’t just restrict marriage to families. It teaches us about the honor due to pro-creative, exclusive, life-long partnerships.

When the laws change, they teach a new lesson. Sometimes the lesson is superficial — a speeding limit adjustment, for instance — and sometimes it isn’t. But laws have consequences.

By redefining marriage to include homosexuals, a state may very well mean to teach the lesson that homosexuals shouldn’t suffer unjust discrimination. That’s a good lesson to teach, though we would argue that current marriage laws aren’t unjust.

But at the same time, the state would teach another lesson even more profoundly. Marriage isn’t the protection we give to those who want to bring children into the world. It’s merely a benefits arrangement for lovers.

And what will follow from that? The very foundation of our society would be eroded.

So the Senate may have had the most important vote of the year already this year. Find out how your senators voted, and in November, remember.