What Is Marriage?: Man and Woman: A Defense
If the law defines marriage to include same-sex partners, many will come to misunderstand marriage. 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. For reasons to be explained, 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.