$\forall$$T$:Type, $A_{1}$, $A_{2}$, $B_{1}$, $B_{2}$:($T$$\rightarrow$$T$$\rightarrow\mathbb{P}$). $A_{1}$ $\Leftarrow\!$ $A_{2}$ $\Rightarrow$ $B_{1}$ =$>$ $B_{2}$ $\Rightarrow$ \{$A_{1}$ =$>$ $B_{1}$ $\Rightarrow$ $A_{2}$ =$>$ $B_{2}$\}