Diamonds and corkscrews: a hybrid account of realization
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Contemporary work in the metaphysics of realization has produced two central theories as to what it is for an individual to realize a kind. According to the ‘flat theory’ of Lawrence Shapiro, an individual realizes some kind by exemplifying or instantiating the properties that define realizations of that kind. With Carl Gillett’s, ‘dimensioned theory’, on the other hand, an individual takes part in the realization of some kind merely by contributing causally towards the properties that define realizations of that kind. Both views are vulnerable to objections. Flat realization is focused on the realization of functional kinds, and, therefore, is poorly suited to describe the realization of scientific or compositional kinds. The dimensioned view handles compositional kinds very well, but has difficulty delineating limits as to what may count as a causal component for sake of realization. If everything qualifies as a causal component of realization, every individual with different causal components begins to resemble a unique realization. If every individual qualifies as a unique realization, every kind constituted by more than one individual will be constituted by more than one realization. This threatens to trivialize the realization thesis, as every kind becomes multiply realizable. In order to resolve these problems, I develop a two-level theory of realization inspired by Lewis’ ‘Mad Pain and Martian Pain’. According to Lewis, pain should be identified only contingently with the physical properties of typical pain. It is also the case, according to Lewis, that pain should be identified only contingently with the functional properties of typical pain. Accounting for this dual contingency suggests two different ways in which a causal role may be fulfilled. On the one hand, a causal role can be fulfilled in the sense in which an individual’s internal systems and structures are understood to produce certain aggregate, object-level capacities. On the other hand, a causal role can also be fulfilled in the sense in which certain object-level capacities are understood as the instantiation of psychological or conceptual abilities. If these different senses of role fulfilment qualify as different ways of realizing a causal role, there will be different, but compatible, ways in which an individual may be understood to realize a particular kind.