Let $\displaystyle \alpha$ and $\displaystyle \beta$ be two von Neumann ordinals. Show that $\displaystyle \alpha \subset \beta$ if and only if $\displaystyle \alpha \in \beta$.
<= is easy enough
=> is where my mind breaks down...
Let $\displaystyle \alpha$ and $\displaystyle \beta$ be two von Neumann ordinals. Show that $\displaystyle \alpha \subset \beta$ if and only if $\displaystyle \alpha \in \beta$.
<= is easy enough
=> is where my mind breaks down...