The nominal scale is a primitive form, and quite
naturally there are many who will urge that it is absurd
to attribute to this process of assigning numerals
the dignity implied by the term measurement. Certainly
there can be no quarrel with this objection, for
the naming of things is an arbitrary business. However
we christen it, the use of numerals as names for
classes is an example of the "assignment of numerals
according to rule." The rule is: Do not assign the
same numeral to different classes or different numerals
to the same class. Beyond that, anything goes with
the nominal scale