1. $T$ : Type
\\[0ex]2. $T$ List
\\[0ex]3. $P$ : \{$x$:$T$$\mid$ ($x$ $\in$ [])\} $\rightarrow\mathbb{P}$
\\[0ex]4. $\forall$$x$$\in$[]. Dec($P$($x$))
\\[0ex]$\vdash$  $\exists$${\it L'}$:$T$ List. (${\it L'}$ $\subseteq$ [] \& ($\forall$$x$:$T$. ($x$ $\in$ ${\it L'}$) $\Leftarrow\!\Rightarrow$ (($x$ $\in$ []) \& $P$($x$))))