D oes marriage need defending? If so, against what? Should the institution of marriage, no less than our individual marriages, be celebrated, as a great, enduring success story? And if so, why? A surprising number of political activists, policy analysts, community leaders, legal scholars, philosophers, theologians, social scientists, and moralists of all stripes see a great deal to celebrate in the institution of marriage, and likewise, see all sorts of threats against which it needs defending. Precisely what the celebrants of marriage are celebrating, however, and what threats they see when they defend it are very different, depending on what they understand the institution of marriage to be. In fact, what promarriage activists and scholars see, defend, and celebrate, when they look at marriage, is so different, they are often arguing at cross purposes with each other, no less than with their joint antagonists.