Sexual Intercourse, Old School

At Doug Wilson's Blog and Mablog, you'll find a fine, succinct account of marriage biblically defined. Here's a clipping:

A marriage requires two components or elements. The first is old school sexual intercourse and the second is a socially recognized set of vows, committing the couple to a legally recognized and protected state of marriage. If one or the other is missing, then so is the marriage. 

To use the language of philosophy, each of these is a necessary condition for marriage (without which, not), but not a sufficient condition. In other words, you can't have a marriage without the presence of both of these elements, but the mere presence of one of them does not constitute or create the marriage. The absence of either will result in no-marriage, but the presence of either does not automatically result in marriage. You must have both together. 

The first element is the one flesh union (Gen. 2:24).
And the first thing to note is that it is possible to be sexually immoral without a one flesh union occuring. This occurs, for example, with porn, or with heavy petting, or with oral sex, etc. So the one flesh union is not defined by the presence of one or more orgasms; it is defined by a heterosexual sexual union, as classically understood. If Christians allow their definitions of the one flesh union to broaden, such that it includes "messing around," the problem is that homosexuals can mess around also, and in exactly the same ways. Only heterosexuals can be married because only heterosexuals can perform the central act that is necessary to the establishment of marriage. Homosexuals can't be married for the same reason that bolts are useless without nuts -- key equipment is missing. 

The second element would be the vows, legally recognized as such. By vows I do not mean the promises that Billy breathes into Sally's albaster ear in the back seat of the car, to wit, promises to love her "forever and a day." I mean vows and promises that are recorded, however their society records such things, and which are enforceable should one or the other of the parties try to walk away from their promises.

To read the whole post, as I said, Blog and Mablog.