theorem
  H is universal implies for f holds (f in St(the_scope_of H,E) & for g
  st for y st g.y <> f.y holds bound_in H = y holds g in St(the_scope_of H,E) )
  iff f in St(H,E)
proof
  assume H is universal;
  then H = All(bound_in H,the_scope_of H) by ZF_LANG:44;
  hence thesis by Th6;
end;
