existse{-}le(${\it es}$;${\it e'}$;$e$.$P$($e$)) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\exists$$e$:es{-}E(${\it es}$). (es{-}le(${\it es}$; $e$; ${\it e'}$) c$\wedge$ $P$($e$))