So, I was derping around on the internets and I ran into an article with the following portentous title: "A Rational Basis for Marriage between One Man and One Woman." Curious, I read on. Here's how it begins:
It is imperative for Catholics to develop rational arguments to defend the institution of marriage in the public square. We live in a pluralistic society and, therefore, what we accept as revelation is not necessarily accepted by others. However, an argument grounded in right reason—without explicit recourse to revelation—is in principle comprehensible to all persons of good will.
I'm all in agreement. It continues:
As we consider the current debate over marriage, it would be a mistake to underestimate the pedagogical function of the law and how a fundamental change in marriage law will result in a fundamental change in our understanding of the human person. What is at stake in the push to redefine marriage to include same-sex partners is not only the radical redefinition of marriage—but, also and necessarily, the radical redefinition of the human person and the entire range of relationships that constitute our basic experience as persons: male and female; husband and wife; mother and father; son and daughter; brother and sister.
Well, that's a bad sign–there's going to be a slippery slope! But that's not what interests me about this piece. It's the following two paragraphs (directly from above):
Marriage between one man and one woman is recognized as a public institution, with its attendant benefits and responsibilities, precisely because it serves the common good. Marriage offers the State its most necessary common good: bringing children into the world and raising them in a family that includes the love of their mother and father. The State needs people (citizens) in order to flourish: no people = no State. Under the principle of subsidiarity, the common good is better served when mothers and fathers raise their children, not the State.
Extending marriage to same-sex partners will redefine marriage in such a way that marriage will no longer be understood to have a direct relationship to the procreation and education of children. Bringing children into the world and raising them will be seen as extrinsic rather than intrinsic to marriage. Openness to procreation will no longer belong to the very substance and definition of marriage. It will be reduced merely to an option for those couples who happen to want children.
If you're playing along at home, the first paragraph seems to suggest that it's either Trad Marriage (by the principle of WTF) or the STATE RAISES YOUR BABIES. It also seems to allege that there will be no babies without marriage. But forget about that. The second of the two rests on a couple of key instances of the passive voice: will be understood and will be seen. Well, I wonder, by whom? Let's rewrite the passage in the active voice:
Extending marriage to same-sex partners will redefine marriage in such a way that [rewrite: some people, catholics, etc. will no longer understand] marriage to have a direct relationship to the procreation and education of children. [rewrite: These people will see ] that Bringing children into the world and raising them [is] extrinsic rather than intrinsic to marriage. Openness to procreation will no longer belong to the very substance and definition of marriage. It will be reduced merely to an option for those couples who happen to want children.
The passive voice just covers up all of the questions being begged. Marriage, in its public legal sense, has many definitions. In some states, this already includes same-sex marriages. As a public institution, therefore, it has "no substance and definition" in some kind of robust metaphysical sense, as the use of the passive suggests. People see marriage in all sorts of ways, and they define it as a public institution in different ways. Some people may "understand it to be x" but that doesn't mean that they understand it correctly. Nor for that matter does it mean that they aren't fully entitled to live it that way.
If you want to make openness to procreation a part of your marriage, then get married in a Catholic Church. If you don't care, as some already don't, then don't. Catholics do not own the definition of marriage as a secular and public institution. If you're going to make an appeal to reason, right or otherwise, you cannot presume without argument that your view is the starting point.