Given their importance in the history of ideas, monistic theories of society have received little serious attention in the literature. By a monistic theory, I mean one which holds that in a given area, one factor (or variable, as I shall usually call it) determines everything that happens; or, less strictly, that the one variable is the most important or crucial one in determining what happens in the given domain. There are social theories which hold, for example, that ideas are the only or crucially determining factor in history and theories which hold that certain ones among our ideas - religious or philosophical or scientific - constitute that factor. Other theories have maintained that a certain biological factor such as race or size is the major factor in the social process.