In their book What Is Marriage? Man and Woman: A Defense, Sherif Gergis, Ryan T. Anderson, and Robert P. George defend the historic understanding of marriage as the conjugal union of husband and wife.

At its essence, they argue, marriage is a comprehensive union—

  • a union of will (by consent) and body (by sexual union);
  • inherently ordered to procreation and thus the broad sharing of family life; and
  • calling for permanent and exclusive commitment, whatever the spouses’ preferences.

If the law defines marriage to include nonmarital relationships (such as same-sex partners), then many people will come to misunderstand marriage, which is not only a personal and social reality but also a moral reality—that is, “a human good with an objective structure, which it is inherently good for us to live out.”

Recognizing such relationships as a “marriage” would “obscure the shape, and so weaken the special norms, of an institution on which social order depends.”

They will not see it as essentially comprehensive, or thus (among other things) as ordered to procreation and family life—but as essentially an emotional union.

. . . they will therefore tend not to understand or respect the objective norms of permanence or sexual exclusivity that shape it.

Nor, in the end, will they see why the terms of marriage should not depend altogether on the will of the parties, be they two or ten in number, as the terms of friendships and contracts do.

In summary, to the extent that people misunderstand the true definition of marriage, to that extent:

  • It will be harder to see the point of marital norms.
  • It will be harder to live by marital norms.
  • It will be harder to urge others to live in accordance with these norms.