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