Kerodon

\begin{equation} \begin{gathered}\label{equation:cartesian-natural-transformation} \xymatrix { \mathscr {F}(x) \ar [r]^{ \mathscr {F}(e) } \ar [d]^{ \gamma _ x } & \mathscr {F}(y) \ar [d]^{ \gamma _{y} } \\ \mathscr {G}(x) \ar [r]^{ \mathscr {F}(e) } & \mathscr {G}(y) } \end{gathered} \end{equation}