$\forall$$T$:Type, $R$:($T$$\rightarrow$$T$$\rightarrow\mathbb{P}$), $a$, $b$:$T$. ($R$$\backslash$)($a$,$b$) = ($R$($a$,$b$) \& ($\neg$($R$($b$,$a$)))) $\in$ $\mathbb{P}$