ABSTRACT
In Chapter I we identified sets according to their cardinal number; an attribute we want to consider next is that of order. For instance, we want to distinguish between the sets A = {1,2,…} ordered by the usual “≤” relation and B = {…,2,1} ordered by “≥.” Although these sets are equivalent in the sense of cardinality, the same is not true if we take the order into account: A has a first, but not a last, element, and B has a last, but not a first, element.
