For example, Mrs. Sanger's pamphlet on birth control, which is addressed to working women, was declared obscene on the ground that working women could understand it. Dr. Marie Stopes's books, on the other hand, are not illegal, because their language can only be understood by persons with a certain amount of education. The consequence is that, while it is permissible to teach birth control to the well-to-do, it is criminal to teach it to wage-earners and their wives.
出典： Bertrand Russell :Marriage and Morals, 1929
Source: Bertrand Russell :Marriage and Morals, 1929
More info.: https://russell-j.com/beginner/MM08-150.HTM