There is no requirement that the relationship between quiddities and dispositions must hold with metaphysical necessity for quiddities to be physically efficacious

In response to the first version of that objection, on which quiddities lack physical efficacy, some reject the assumption that any such conclusion follows from the premise that a single type of physical disposition might have been grounded by a distinct quiddity from the quiddity that actually grounds it (Hawthorne 2002, Alter and Coleman forthcoming). Causal relations, it is argued, do not in generally hold with metaphysical necessity. So, why must the relationship between quiddities and dispo