 The first response is that \(\exists{R}\) ranges over classes but that some classes are too large (or otherwise unsuited) to be sets. In particular,  (13)  asserts the existence of the Russell-class, which isn’t a set. This response has been found problematic because it postulates the existence of different kinds of “set-like” entities (Boolos 1984: 442 [1998a: 66] and 1998b: 35). It has also been objected that this response only postpones the problem posed by  (13).  For it would also be true that