theorem Lem00:
  the_sort_of @r = the_sort_of r
  proof
    the Sorts of T is MSSubset of Free(S,X) by MSAFREE4:def 6;
    then @r in (the Sorts of T).the_sort_of r
    c= (the Sorts of Free(S,X)).the_sort_of r by SORT,PBOOLE:def 2,def 18;
    hence thesis by SORT;
  end;
