無限公理(>>220-221)https://en.wikipedia.org/wiki/Axiom_of_infinity Axiom of infinity で、”A consequence of this definition is that every natural number is equal to the set of all preceding natural numbers. The count of elements in each set, at the top level, is the same as the represented natural number, and the nesting depth of the most deeply nested empty set {}, including its nesting in the set that represents the number of which it is a part, is also equal to the natural number that the set represents.” と説明しているのは、Neumannの後者関数の有限ｎにおける二つの性質 1）それ以前の集合を合わせたもの、2）{}までの深さカッコの深さがｎ この二つの性質を、Axiom of infinityで出来た自然数の集合Nは、受け継ぎ極限 n→∞�
