Russell’s “No-Class” theory of classes from *20 of Principia Mathematica provides a contextual definition like that of the theory of definite descriptions. One of Russell’s early diagnoses of the paradox of the class of all classes that are not members of themselves was that it showed that classes could not be individuals. Indeed Russell seems to have come across his paradox by applying Cantor’s famous diagonal argument to show that there are more classes of individuals than individuals. Hence,