I received such a volume of feedback on Part One, including a collection of very intelligent critiques and questions, that I am postponing my original plan to delve straight into the life and social implications of the traditional view of marriage, and will instead devote this post to responding to them to the best of my ability. I've tried to arrange them into a natural progression from one thought to the next. (Special thanks to my friends Dave Brown and Aaron Hershkowitz for their assistance.)*
What distinguishes civil marriages from sacramental marriages?
A civil marriage is a natural marriage rather than a sacramental one. Marriage as a sacrament is something specific to the Church, and was instituted by Christ (cf. Matthew 19.3-12, Ephesians 5.25-32), to confer grace on the participants, which is the purpose of every sacrament. However, in so doing, He did not abolish the institution of natural marriage -- otherwise it would be immoral for anybody but Christians to get married, which is patently absurd. Every sacramental marriage is therefore a natural marriage, but not all natural marriages are sacramental. I am given to understand that there is debate among theologians as to whether a natural marriage can be dissolved by divorce; the laws laid down in the Torah suggest that it could. The Church teaches that a sacramental marriage cannot be dissolved by anything but death. (Annulments are something else again, which I touch on further down.)
The argument is that gay marriage (or, strictly speaking, its underlying assumptions) tries to alter the definition of marriage, but isn't that what the Catholic Church has done in making marriage a sacrament?
A very good question, to which the answer is, of course, yes and no. More simply, the answer is no. The principle here was enunciated by St. Thomas Aquinas: grace does not destroy nature, but perfects it (gratia non tollit naturam sed perficit, for you Latin fiends out there). The Catholic notion of sacramental marriage does not do away with natural marriage in its own right. More importantly, while it deepens the significance of marriage for Christians, it takes natural marriage as its premise: it adds meaning, but takes no meaning away. The modern idea of reducing marriage to a celebration of romantic love is precisely that, a reduction -- it takes away one of the purposes of marriage. The sacramental idea keeps all the previous purposes of marriages, and then infuses the institution with a supernatural in addition to a natural significance.
If man is made for love, then how can identifying marriage simply with love be a bad thing?
For much the same reason that identifying government with love is a bad thing. Love is a good thing (provided, of course, that we define what we mean by the term), and man is called to love in every circumstance and institution life involves; but this does not mean that everything draws its meaning simply from love, unmodified. I personally would go to great lengths to avoid the Ministry of Love, if it came to that. (I don't think there's a moral equivalency between this altering of the social significance of marriage and a bureaucratic "love," naturally -- it is the logical parallel that I am citing, not a similarity of degree.)
More specifically, it is the identification of marriage with romantic love that is problematic. Romantic love is of course a good and beautiful thing, but it is not intrinsically connected to either marriage or family (though I do think it a good thing to have is as a prelude to both): many, if not most, families in history have come into being without, or before, the intervention of romance in their lives. The love for which man is meant is supernatural love -- participation in the life of the Trinity, what the Eastern Orthodox (in the language of St. Peter) refer to as theosis or divinization. This is not identical with any kind of natural love, nor with any institution; they can serve as means to it, but only if we choose to use them in that fashion -- which means using them according to their natures.
Since the state performs civil marriages (e.g., between divorced parties) that couldn't be sacramental marriages, doesn't this mean that it could equally perform gay marriages even though these couldn't be sacramental?
No. The reason here is that it is precisely the character of natural marriage, according to the natural law thesis, that prevents couples intrinsically unable to procreate from entering it; the Scriptural prohibitions would reaffirm this, but the principle is derived from the essence of marriage with or without the sacraments, not from a specially religious imprint upon sacramental marriage.
If the appeal here is to natural law, as understood by the Catholic Church, should there be civil restrictions on contraception too?
I don't know. I am strongly inclined to say no, out of respect for personal privacy; but I don't know exactly how far the state ought to go in enforcing even natural morality upon its citizens. (This may seem like an ironical attitude in the first place for someone with professedly anarchist symapthies, but here, I'm working on the assumption that -- whether as affirmation or as concession -- there is a state, and trying to determine where its power to make a nuisance of itself needs to be stopped.) My general disposition is that, while society in general should acknowledge more ethical strictures than this, the law per se ought probably to recognize only two: consensuality and breach of covenant, i.e. adultery (this latter only on the grounds suggested by C. S. Lewis in Present Concerns, where he pointed out that it violates the principle that "men make their covenants"; that the violation happens to be sexual would not be the important thing). However, I am open to further education on this point, as I am ignorant of the consensus of theologians (if there is one) on the subject, and haven't worked out my own philosophy thoroughly on this point.
To digress slightly, it is worth saying that there ought -- not simply on Christian grounds, I think, but on grounds of common sense -- to be a much more serious attitude toward marriage generally as a secular institution, especially among Christians. The ease of divorce in this country has done considerably more damage to marriage than gay marriage is ever likely to, and it gravely discredits the Church's witness that she has done virtually nothing to encourage a stronger character for civil marriage in the face of rampant divorce. The harm done to society, especially to children, by this casual acceptance of divorce is profound, and will take generations to repair, even supposing we start right now and don't stop.
If marriage is intrinsically oriented toward the begetting of children, what about marriages that are never consummated, married couples who choose not to have children, or people who marry after childbearing age?
A very intelligent critique. Three distinct issues to be addressed.
Marriages that are never consummated are, from a Catholic perspective, open to annulment, i.e. a declaration that a supposed marriage never in fact took place, because one of the essential ingredients was lacking. These essential ingredients include but are not limited to: free consent, together with the age and maturity required to give such consent; sufficient biological distance between the parties that the marriage is not incestuous; the intention of fidelity; openness to children; and, after the union is performed, consummation -- which is why the word consummation is used. There are legal annulments as well, though I don't know their conditions, not being closely acquainted with American law (or distantly acquainted with it, actually).
Married couples who never intend to have children, in my view, are really entering into a civil union rather than a marriage properly so-called. Ideally, they would do so. I don't know how possible it would be for this principle to be enforced, though: it seems intrusive to ask a couple, before granting them a marriage certificate, whether they intend to have children. (In the style of the brilliant and neglected C. Northcote Parkinson, "How many children have you and why? Have you had chicken pox and why not? The penalty for a false declaration is life imprisonment.") Additionally, it would be perfectly easy for a couple in that position to lie, so that the practical prospect of enforcement seems a dim one.
Those who enter into marriage after childbearing age pose a more delicate difficulty. The Bible of course records multiple miracles of fertility, of which the most famous is probably that of St. Elizabeth, the mother of St. John the Baptist. But this would properly form part of a case in favor of the Church permitting sacramental marriages for those of advanced age, not a case for recognition from the secular state, since we have been working on the premise that revelation is outside the state's purview. I think the answer is that a medical advance could in principle redress the decay of fertility, and therefore it would in principle be possible for such a couple to have children -- though perhaps inadvisable. Conversely, a homosexual couple, whatever their other virtues, could not bring forth children no matter how much their health was improved, save by changing the terms of the problem (e.g. through surrogate motherhood, in vitro, or a sex change). Once again, I am quite amenable to further instruction on this point.
*Readers who notice that sort of thing may observe that I have left aside my usual habit of quoting from the King James, and instead made reference to the English Standard Version. This is because I quote the King James for aesthetic reasons rather than strict theological and linguistic accuracy. Though it regrettably doesn't have a Catholic edition (or, as I'm fond of calling it, the director's cut), the ESV is the most accurate translation of the Bible with which I'm acquainted, though the NAB and the RSV are more popular in many Catholic circles.
Preface for Paschaltide
It is very meet, right, and our bounden duty, that we should at all times, and in all places, give thanks unto thee, O Lord, holy Father, almighty, everlasting God; but chiefly are we bound to praise thee for the glorious Resurrection of thy Son Jesus Christ our Lord; for he is the very Paschal Lamb, who was sacrificed for us, and hath taken away the sin of the world; who by his death hath destroyed death, and by his rising to life again hath won for us everlasting life.