ABSTRACT
A set or class is a collection of elements. Those elements belong to the set and are known as its members, and those members may themselves be sets. Clearly the set of Frenchwomen is not a member of itself: what determines this is whether or not the set has its defining property, the property of being a Frenchwoman. The set of sets, on the other hand, does seem to be a member of itself, since it is a set.
