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What would a game look like that is everywhere bounded by rules? - We could imagine tightening up the rules of tennis. We could specify that the ball must not be thrown more than four metres into the air when serving. But that would leave various other aspects unbounded by rules. How many times is someone allowed to bounce the ball on the ground before they serve?

Wittgenstein seems to contemplate the possibility that this might lead to an infinite regress. We could have a rule to regulate the application of a rule which removes some doubt but would this then stand in need of a further rule to regulate its application?

But it need not be that we are in doubt because we could imagine a doubt. (-Interesting epistemological point here which could serve as a reminder in other areas - relevant to Descartes' method of doubt).