$\forall$$T$:Type, $R$:($T$$\rightarrow$$T$$\rightarrow\mathbb{P}$), $x$, $y$:$T$. ($x$ ($R$$^{\mbox{\scriptsize $\ast$}}$) $y$) $\Leftarrow\!\Rightarrow$ (($x$ $R$\^{}+ $y$) $\vee$ ($x$ = $y$))