Let be a continuous function of an interval into itself. The period of a point in is the least integer for which . If has period 3 then the relation (or its reverse) is satisfied for one of the points , , or . The title of the paper derives from the theorem that if some point in has this Sysiphusian feature, “two steps forward, one giant step back”, then has periodic points of every period . Moreover, contains an uncountable subset devoid of asymptotically periodic points, such that
for all in . (a point is asymptotically periodic if for some periodic point .) The proof is eminently accessible to the nonspecialist and is therefore of interest to anyone modeling the evolution of a single population parameter by a first order difference equation. The authors compare the logistic with a model of which, by contrast, wherever the derivative exists. For such a system no periodic point is stable, in the sense that for all in a neigborhood of a periodic point of . A brief survey of a theorem motivated by ergodic theory completes this fascinating paper.