In this comment, I see that Mauro Allegranza and I were saying the same thing as shown in the table below:
| Allegranza | Zeynel |
|---|---|
| $0 \in T$ | $0 \in T$ |
| $n \in T$ | $n \in T$ |
| $S(n) \in T$ | $S(n) \in T$ |
| $ T = \mathbb{N}$ | $T$ contains all natural numbers |
Allegranza claims my version is not correct. But to me "$ T = \mathbb{N}$" and "$T$ contains all natural numbers" are identical statements. Is there a difference I don't understand?
$T=\Bbb{N}$ means that $T\subseteq\Bbb{N}$ and $\Bbb{N}\subseteq T$. On the other hand, the statement "$T$ contains all natural numbers" only means that $\Bbb{N}\subseteq T$.
Therefore, "$T=\Bbb{N}$" and "$T$ contains all natural numbers" are different statements.