Could civil unions be good for marriage?

My student Phil Steger offered the following response to my question about the impact of civil unions on marriage:

It is possible that an increase of civil unions may actually strengthen the institution of marriage by distinguishing contractual partnerships made for mutual benefit from sacramental unions that bear witness to divine reality and provide a "school of love" (to borrow St. Benedict's term) through which two people can labor toward holiness. People can then make a clear and conscious choice between the two, based on their actual intent and motive for joining their life with another person.

This, to me, is the key distinction between civil unions and marriage. Both civil unions and marriages can provide a stable framework for having and raising children. And both civil unions and marriages can also be childless. The sociological argument for marriage--it's best for children and the social order--is important, but it is not the heart of the meaning and reality of marriage, at least as illuminated by revelation and tradition.

In the Bible, the structure of marriage and its role in creating or contributing to the social order are somewhat fluid. What is consistent in the Bible, as well as the Apostolic and Patristic sources, is marriage a potent sign of God's love and union with his people. It encourages our faith in the biblical promise that we are each created for perfect union in God, by showing us examples of how two people can grow deeply in union with each other, even in our fallen state. It also provides a training ground of self-giving and self-denial for cultivating the practices and dispositions to prepare us for our destiny of union in God. It resembles the Eucharist and the Liturgy in these ways: as living signs of spiritual reality and as "arenas" in which to practice living according to that reality.

There is no question that the potential for children and family are the natural outgrowth of this union. But this potential doesn't become actual in every marriage. The sacramental union, on the other hand, is actually present in every marriage, though its fullness remains a potentiality requiring commitment and effort and grace to develop. Neither the actuality, nor even the potential, for this sacramental union is ever present in civil unions, even though the potential for children and family are.

I question whether our anxious concern for the sociology of marriage is obscuring our faithful witness to its sacramentality, which might do more to undermine marriage then civil unions. I think if we Catholics were to begin there, our encounters with both civil unions, same or opposite sex, and same-sex marriage, would cause us less fear and anxiety over the fate of marriage. It might also equip us with greater discernment about the essential truths of marriage that we want to preserve and protect and how best to do so.