Causal Structuralism, Dispositional Actualism, and Counterfactual Conditionals

Dispositional essentialists are typically committed to two claims: that properties are individuated by their causal role (‘causal structuralism’), and that natural necessity is to be explained by appeal to these causal roles (‘dispositional actualism’). I argue that these two claims cannot be simultaneously maintained; and that the correct response is to deny dispositional actualism. Causal structuralism remains an attractive position, but doesn’t in fact provide much support for dispositional essentialism. 1 Properties and Modality It is a truism that objects act as they do at least in part because of how they are. Though there may be outside forces that influence how the object behaves, the most significant determiners of that behaviour are the intrinsic properties that the object itself possesses. The role of properties in determining behaviour is so important that we frequently individuate properties by the characteristic behaviours to which they give rise. This is most obvious in the case of dispositions: fragility, for example, just is that property which contributes the characteristic behaviour of breaking when appropriately struck to its possessors. Orthodox Humean views hold that the connection between properties and behaviour, even in the case of dispositions, is contingent. For example, Lewis adopts a modern version of Hume’s denial of necessary connections when he advocates a principle of recombination according to which patching together parts of different possible worlds yields another possible world. (Lewis, 1986: 87–8)