), then classes having 2 terms, and so on. We thus get a progression of sets of sub-classes, each set consisting of all those that have a certain given finite number of terms. So far we have not used the multiplicative axiom, but we have only proved that the number of collections of sub-classes of
is a reflexive number, i.e. that, if
is the number of members of
, so that
is the number of sub-classes of