[foldr]

The issue isn't the difficulty of the concept but the ambiguity of "best strategy".

[murbard2]

Fine, best strategy given a perfectly rational opponent. There, ambiguity removed.

[foldr]

Well not quite, you also need to specify that the opponent assumes that you are perfectly rational, and that he assumes that you assume that he is, and that he assumes that you assume that he assumes that you are, and so on. A perfectly rational opponent would not assume that you are perfectly rational in the absence of any relevant information. Rather, he would assume that his opponent was equally likely to be using any strategy.