Example 9.2.3.3 ($\infty $-Categories). Let $\operatorname{\mathcal{C}}= \operatorname{Set_{\Delta }}$ be the category of simplicial sets and let $W$ be the collection of all inner horn inclusions $\Lambda ^{n}_{i} \hookrightarrow \Delta ^ n$, where $0 < i < n$. Then a simplicial set is weakly $W$-local if and only if it is an $\infty $-category.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$