 The games here are the same as in the previous section, except that we drop the assumption that each player knows the previous history of the play. For example we can require a player to make a choice without knowing what choices the other player has made at certain earlier moves. The classical way to handle this within game theory is to make restrictions on the strategies of the players. For example we can require that the strategy function telling \(\exists\) what to do at a particular step is a function whose domain is the family of possible choices of \(\forall\) at just his first and second moves; this is a way of expressing that \(\exists\) doesn’t know how \(\forall\) chose at his third and later moves. Games with restrictions of this kind on the strategy functions are said to be of imperfect information, as opposed to the games of perfect information in the previous section.