Aumann has proved that common knowledge of substantive ratio-nality implies the backwards induction solution in games of perfect information. Stalnaker has proved that it does not. Roughly speaking , a player is substantively rational if, for all vertices v, if the player were to reach vertex v, then the player would be rational at vertex v". It is shown here that the key diierence between Auma...

A version of the classical secretary problem is studied, in which one is interested in selecting one of the b best out of a group of n differently ranked persons who are presented one by one in a random order. It is assumed that b ≥ 1 is a preassigned number. It is known, already for a long time, that for the optimal policy one needs to compute b position thresholds, for instance via backwards ...