# Kerodon

$\Newextarrow{\xRightarrow}{5,5}{0x21D2}$

Remark 5.5.1.5. Let $f: X \rightarrow Y$ be a morphism of Kan complexes. Then $f$ is a homotopy equivalence (in the sense of Definition 3.1.5.1) it and only if it is an isomorphism when viewed as a morphism of the $\infty$-category $\operatorname{\mathcal{S}}$.