 In M this is once again equivalent to (P.4), but the equivalence depends on Reflexivity and Symmetry. Absent (P.1) or (P.2), (P.4′) is logically stronger. Yet again one may rely on the alternative definition of ‘PP’ to obtain variants of (P.4′) that are stronger than (P.4c) and weaker than (P.4). Similarly for (P.4d), which may be further weakened or strengthened by tampering with the parthood predicates occurring in the antecedent and in the consequent.