Kerodon

$\Newextarrow{\xRightarrow}{5,5}{0x21D2}$ $\newcommand\empty{}$
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$

Example 4.7.3.21. Let $\aleph _0$ be the least infinite cardinal. Then $\aleph _0$ is strongly inaccessible. That is, the collection of finite sets is closed under finite products.