68. "All right: the concept of number is defined for you as the logical sum of
these individual interrelated concepts: cardinal numbers, rational numbers, real
numbers, etc.; and in the same way the concept of a game as the logical sum of a
corresponding set of sub-concepts."—It need not be so. For I can give the
concept 'number' rigid limits in this way, that is, use the word "number" for a
rigidly limited concept, but I can also use it so that the extension of the
concept is not closed by a frontier. And this is how we do use the word "game".
For how is the concept of a game bounded? What still counts as a game and what
no longer does? Can you give the boundary? No. You can draw one; for none has so
far been drawn. (But that never troubled you before when you used the word
"But then the use of the word is unregulated, the 'game' we play with it is unregulated."—It is not everywhere circumscribed by rules; but no more are there any rules for how high one throws the ball in tennis, or how hard; yet tennis is a game for all that and has rules too.