ABSTRACT
There is a traditional distinction between “proper” names and “class” names, which is explained as consisting in the fact that a proper name applies, essentially, to only one object, whereas a class name applies to all objects of a certain kind, however numerous they may be. Thus “Napoleon” is a proper name, while “man” is a class name. It will be observed that a proper name is meaningless unless there is an object of which it is the name, but a class name is not subject to any such limitation. “Men whose heads do grow beneath their shoulders” is a perfectly good class name, although there are no instances of it. Again, it may happen that there is only one instance of a class name, e.g. “satellite of the earth”. In such a case, the one member may have a proper name (“the moon”), but the proper name does not have the same meaning as the class name, and has different syntactical functions. E.g. we can say: “ ‘Satellite of the earth’ is a unit class”, but we cannot say “the moon is a unit class”, because it is not a class, or at any rate not a class of the same logical type as “satellite of the earth”, and if taken as a class (e.g. of molecules) it is many, not one.
