This means that a player cannot know that her opponent will not choose an action at a state \(w\) which is deemed rational (according to some choice rule). This property is called “privacy of tie-breaking” by Cubitt and Sugden (2011: 8) and “no extraneous beliefs” by Asheim and Dufwenberg (2003).[16]  For an extended discussion of the above assumption see Cubitt &amp; Sugden (2011).