If marriage is the great mystery of the City, the image of the Coinherence - if we do indeed become members one of another in it - then there is obviously going to be a fundamental need in marriage for two people to be able to get along with each other and with themselves. And that is precisely what the rules of human behavior are about. They are concerned with the mortaring of the joints of the City, with the strengthening of the ligatures of the Body. The moral laws are not just a collection of arbitrary parking regulations invented by God to make life complicated; they are the only way for human nature to be natural.
For example, I am told not to lie because in the long run lying destroys my own, and my neighbor's nature. And the same goes for murder and envy, obviously; for gluttony and sloth, not quite so obviously; and for lust and pride not very obviously at all, but just as truly. Marriage is natural, and it demands the fullness of nature if it is to be itself. But human nature. And human nature in one piece, not in twenty-three self-frustrating fragments. A man and a woman schooled in pride cannot simply sit down together and start caring. It takes humility to look wide-eyed at somebody else, to praise, to cherish, to honor. They will have to acquire some before they can succeed. For as long as it lasts, of course, the first throes of romantic love will usually exhort it from them, but when the initial wonder fades and familiarity begins to hobble biology, it's going to take virtue to bring it off.
Again, a husband and a wife cannot long exist as one flesh, if they are habitually unkind, rude, or untruthful. Every sin breaks down the body of the Mystery, puts asunder what God and nature have joined. The marriage rite is aware of this; it binds us to loving, to honoring, to cherishing, for just that reason. This is all obvious in the extreme, but it needs saying loudly and often. The only available candidates for matrimony are, every last one of them, sinners. As sinners, they are in a fair way to wreck themselves and anyone else who gets within arm's length of them. Without virtue, therefore, no marriage will make it. The first of all vocations, the ground line of the walls of the New Jerusalem is made of stuff like truthfulness, patience, love and liberality; of prudence, justice, temperance and courage; and of all their adjuncts and circumstances: manners, consideration, fair speech and the ability to keep one's mouth shut and one's heart open, as needed.
And since this is all so utterly necessary and so highly likely to be in short supply at the crucial moments, it isn't going to be enough to deliver earnest exhortations to uprightness and stalwartness. The parties to matrimony should be prepared for its being, on numerous occasions, no party at all; they should be instructed that they will need both forgiveness and forgivingness if they are to survive the festivities. Neither virtue, nor the ability to forgive the absence of virtue are about to force their presence on us, and therefore we ought to be loudly and frequently forewarned that only the grace of God is sufficient to keep nature from coming unstuck. Fallen man does not rise by his own efforts; there is no balm in Gilead. Our domestic ills demand an imported remedy.