Think only of what the cases are || the sort of cases in which we say that a game is played according to a particular rule.
     The rule may be an aid to instruction || instructing people in the game. The person learning || pupil is told the rule and is trained in its application. || to apply it. – Or it is an instrument || implement of the game itself. – Or: a || a rule is used neither in instruction || teaching the game nor in the game itself; nor is it laid down || included in a book of rules. You learn the game by watching how others play it. But we say it is played according to such and such ¤ rules, because || for a person watching the game can || could read off || derive these rules from the practice of the game || way the game is played, like a natural law || natural laws which the actions of the game follow || players obey. – But howdoes the observer distinguish in this case || , in this case, does the observer distinguish between a mistake on the part of the players || a player and a correct action in the game? There are signs || characteristic signs for this in the behaviour of the players. Think of the characteristic behaviour of someone who has made a slip of the tongue || corrects a slip of the tongue. It would be possible to know that someone was doing || recognise this even if we didn't understand his language.