 Focusing on (iv), the first response is to insist that, on the face of it, a cat and the corresponding lump of feline tissue (or a statue and the lump of clay that constitutes it) do not share the same proper parts after all. For, on the one hand, if one believes that at least one such thing, x, is part of the other, y, then it must be a proper part; and insofar as nothing can be a proper part of itself, it follows immediately that such things do not in fact constitute a counterexample to (29). (This would also follow from Supplementation, as emphasized e.g. in Olson 2006, since the assumption that x and y have the same proper parts entails that no part of y is disjoint from x, at least so long as parthood is reflexive; but there is no need to invoke (P.4) here.) On the other hand, if one believes that neither x nor y is part of the other, then presumably the same belief will also apply to some of their proper parts—say, the cat's tail and the corresponding lump of tissue. And if the tail is not part of that lump, then presumably it is also not part of the larger lump of tissue that constitutes the whole cat (as explicitly acknowledged by some anti-extensionalists, e.g. Lowe 2001: 148 and Fine 2003: 198, n. 5, though see Hershenov 2008 for misgivings). Thus, again, it would appear that x and y do not have the same proper parts after all and do not, therefore, constitute a counterexample to (29). (For more on this line of argument, see Varzi 2008.)