$\forall$$T$:Type, $P$:($T$$\rightarrow$Prop). ($\forall$$x$:$T$. Dec($P$($x$))) $\Rightarrow$ ($\forall$$L$:\{$x$:$T$$\mid$ $P$($x$) \} List, $x$:$T$. ($x$ $\in$ $L$) $\Rightarrow$ ($x$ $\in$ $L$))