reserve i, x, I for set,
  A, M for ManySortedSet of I,
  f for Function,
  F for ManySortedFunction of I;

theorem
  id (bool A) is reflexive MSSetOp of A
proof
  reconsider a = id (bool A) as MSSetOp of A;
  a is reflexive
  by Th8;
  hence thesis;
end;
