The distinguished author of The Mothers here sets himself the task of expounding in popular form the taboo-like nature of our conventional morality of sex, and he succeeds well, for no reader of the book can fail to be impressed by the utter lack of any ultimate foundation in reason or utility for the dictates of this morality. This does not, of course, prevent our moral code from being incidentally useful. But this incidental utility, though it may be seized upon for purposes of rationalization, is psychologically at best a very secondary motive. The best ultimate explanation of why we disapprove of conduct which violates convention is that it is 'disgusting', 'vulgar', 'indecent', 'shocking', and these are—as Mr. Briffault makes abundantly clear—the present-day equivalents and derivatives of savage taboo. In so clearly and attractively setting forth this fact, Mr. Briffault has carried out a useful piece of work. For until the persistence, the limitations, and the disadvantages of taboo have been