 Case (iii) is more delicate, as it depends on one's metaphysics of such things as committees, teams, and groups generally. If one denies that the relevant structural relation is a genuine case of parthood (see Section 1, ad (11)), then of course the counterexample misfires. If, on the other hand, one takes groups to be bona fide mereological composites—and composites consisting of enduring persons as opposed to, say, person-stages, as in Copp (1984)—then a lot depends on one's reasons to treat groups with co-extensive memberships as in fact distinct. Typically such reasons are just taken for granted, as if the distinctness were obvious. But sometimes informal arguments are offered to the effect that, say, the coextensive Library Committee and football team must be distinguished insofar as they have different persistence conditions, or different properties broadly understood. For instance, the players of the team can change even though the Committee remains the same, or one group can be dismantled even though the other continues to operate, or one group has different legal obligations than the other, and so on (see e.g. Moltmann 1997). If so, then case (iii) becomes relevantly similar to case (iv). There, too, the intuition is that a living animal such as a cat is something “over and above” the mere lump of feline tissue that constitutes its body—that they have different survival conditions and, hence, different properties—so it appears that here we have a genuine counterexample to mereological extensionality (via Leibniz's Law). It is for similar reasons that some philosophers are inclined to treat a vase and the corresponding lump of clay as distinct in spite of their sharing the same proper parts—possibly even the same improper parts, contrary to (P.3), as seen in Section  2.2.[14]  Two responses may nonetheless be offered in such cases on behalf of EM (besides rejecting the intuition in question on the basis of a specific metaphysics of persistence).