 Sets are then defined as members, and non-members are labeled “proper classes.” So for example, the Russell class, \(R\), cannot be a member of any class, and hence it must be a proper class. If \(R\) is assumed to be an element of a class \(A\), then it follows from one of von Neumann’s axioms that \(R\) is not equivalent to \(V\). But \(R\) is equivalent to \(V\), and hence not an element of \(A\). Thus, von Neumann’s method is closely related to the result stated above about the set \(R_B\), for arbitrary \(B\). Von Neumann’s method, while admired by the likes of Gödel and Bernays, has been undervalued in recent years. 