theorem Th30:
  X0,X0 do_not_constitute_a_decomposition
proof
  reconsider A0 = the carrier of X0 as Subset of X by TSEP_1:1;
  now
    take A1 = A0, A2 = A0;
    thus A1 = the carrier of X0 & A2 = the carrier of X0 & A1,A2
    do_not_constitute_a_decomposition by Th7;
  end;
  hence thesis;
end;
