might both be the null-class.
Let us illustrate this possibility by an example: Suppose there were exactly nine individuals in the world. (As to what is meant by the word "individual," I must ask the reader to be patient.) Then the inductive cardinals from 0 up to 9 would be such as we expect, but 10 (defined as
) would be the null-class. It will be remembered that
may be defined as follows:
is the collection of all those classes which have a term
