ABSTRACT
Students of history and of biology share a common delight: as they study the details of any subject, they find a fascinating diversity of cases which far exceeds any preconceived expectations. But that is not their sole delight. Some will also see unifying themes therein, with coincidences that beg for explanation and leitmotifs which please the aesthete. Some scholars choose to stress the diversity, perhaps even the perversity, to be found in events in history (or, in biology, of living forms). Other scholars may feel happier following the motto e pluribus unum.
