[The author examines the arguments used by the magisterium against same-sex marriage. Most of these arguments have features that make them problematic for public debate in pluralistic societies. The most plausible argument concerns the health of marriage as an institution within which adults take responsibility for child rearing. If the magisterium wishes to present a more persuasive argument for its position against same-sex marriage, it ought to develop this line of reasoning and jettison the practice of casting gay people in a negative light.]