Suppose we are satisfied that merely fictional entities – like Pegasus – do not exist and that the entities described by natural science – like horses – do. Now consider marriages. To which category do they belong? On the one hand, it seems like a mistake to say that marriages don’t exist, in the manner of Pegasus. Marriage is a real phenomenon, not a mere fiction like Pegasus. But, on the other hand, it seems like a mistake to say that marriages exist, in the manner of horses. Marriages do not exist independently of our social practices, institutions, and conventions – as John Searle puts it, marriages seem to exist only because we believe them to exist.1 So what sort of entities are marriages then?