reserve F,H,H9 for ZF-formula,
  x,y,z,t for Variable,
  a,b,c,d,A,X for set;
reserve E for non empty set,
  f,g,h for Function of VAR,E,
  v1,v2,v3,v4,v5,u5 for Element of VAL E;

theorem
  H is negative implies for f holds not f in St(the_argument_of H,E) iff
  f in St(H,E)
proof
  assume H is negative;
  then H = 'not' the_argument_of H by ZF_LANG:def 30;
  hence thesis by Th4;
end;
