
theorem Th8:
  for S being feasible ManySortedSign holds id the carrier of S, id
  the carrier' of S form_morphism_between S,S
proof
  let S be feasible ManySortedSign;
  per cases;
  suppose
    S is void;
    hence thesis by MSALIMIT:6;
  end;
  suppose
    S is non void;
    then reconsider S as non void feasible ManySortedSign;
    S is non empty;
    hence thesis by PUA2MSS1:28;
  end;
end;
