Judges and justices who reasoned in favor of same-sex marriage based on social scientists' "no differences" thesis must now contend with better research: Heterosexual married couples offer the best family structure for children, according to a new, rigorously researched sociological study. A notable feature of the legal debate over same-sex marriage in the United States in recent years has been the employment of social science research on the family as evidence. In courts of law across the country, advocates of same-sex marriage have advanced the “no differences†thesis—the view that having gay or lesbian parents makes “no difference†in the...