"We are much too much inclined in these days to divide people into permanent categories, forgetting that a category only exists for its special purpose and must be forgotten as soon as that purpose is served. There is a fundamental difference between men and women, but it is not the only fundamental difference in the world. (…) A difference of age is as fundamental as a difference of sex; and so is a difference of nationality. All categories, if they are insisted upon beyond the immediate purpose which they serve, breed class antagonism and disruption in the state, and that is why they are dangerous."