In the present postmodern world, we are told that there is no such thing as a biologically distinct gender. Instead, gender is now socially constructed. It can be defined by the individual in almost any way he or she sees fit. In the old days, many clinical psychologists would have believed that Caitlyn Jenner — who first came to fame as Olympian Bruce Jenner — is experiencing a well-chronicled psychological state known as transvestism, or the innate pleasure in wearing the clothes and assuming the manners and appearance of the opposite sex. Jenner, however, identifies as transgendered. But even if...