const SNo_rec_ii : (set (set set set) set set) set set set const If_i : prop set set set const SNo : set prop const SNo_rec_i : (set (set set) set) set set const Empty : set term SNo_rec2 = \P:set set (set set set) set.SNo_rec_ii \x:set.\g:set set set.\y:set.If_i (SNo y) (SNo_rec_i (\z:set.\f:set set.P x z \w:set.\u:set.If_i (w = x) (f u) (g w u)) y) Empty axiom If_i_0: !P:prop.!x:set.!y:set.~ P -> If_i P x y = y const In : set set prop term iIn = In infix iIn 2000 2000 const SNoS_ : set set const SNoLev : set set var P:set set (set set set) set var x:set var y:set var z:set hyp SNo x hyp y iIn SNoS_ (SNoLev x) claim y != x -> If_i (y = x) (SNo_rec_i (\w:set.\f:set set.P x w \u:set.\v:set.If_i (u = x) (f v) (SNo_rec_ii (\x2:set.\g:set set set.\y2:set.If_i (SNo y2) (SNo_rec_i (\z2:set.\f2:set set.P x2 z2 \w2:set.\u2:set.If_i (w2 = x2) (f2 u2) (g w2 u2)) y2) Empty) u v)) z) (SNo_rec_ii (\w:set.\g:set set set.\u:set.If_i (SNo u) (SNo_rec_i (\v:set.\f:set set.P w v \x2:set.\y2:set.If_i (x2 = w) (f y2) (g x2 y2)) u) Empty) y z) = SNo_rec_ii (\w:set.\g:set set set.\u:set.If_i (SNo u) (SNo_rec_i (\v:set.\f:set set.P w v \x2:set.\y2:set.If_i (x2 = w) (f y2) (g x2 y2)) u) Empty) y z