傾向性の本質主義的理論に向けて : プライア説の批判的検討

Abstract

Elizabeth Prior advanced a theory of dispositions which is still considered to be an orthodox view. The theory has two central theses : (1) dispositions must have causal bases (Causal Thesis); (2) we cannot make any identification of dispositions and causal bases (Distinctness Thesis). These two theses, in combination, bring about a consequence that dispositions are causally impotent (Impotence Consequence). If we accept a plausible tenet that to be real is to possess causal powers, it follows then that dispositions are not real properties. This should be unpleasant even for Prior, as she explicitly commits herself to disposition realism. I try to avoid Impotence Consequence by attacking Distinctness Thesis. Prior presented three arguments for Distinctness Thesis. The first argument relies on the empirical plausibility that a disposition could be multiply realized by various causal bases in various objects. The plausibility of this argument, however, draws on ambiguity about ontology of higher order properties. I offer an ontology of properties, which has particularistic characters and allows us to identify dispositions with their causal bases. Prior's second argument points out that some manifestations of dispositions could be blocked by other properties of the same bearer. This argument, however, overlooks the fact that dispositions need their 'reciprocal partner' dispositions for their manifestations. The third argument relies both on the Kripkean thesis that dispositional predicates are non-rigid designators and on a logical possibility that one and the same disposition might behave differently in a possible world where different natural laws obtain. While accepting the former (Kripkean thesis) , I argue that we are not forced to accept the latter. We can explain the apparent contingency of natural laws by means of objects' contingent possession of dispositions. In section 5, I propose an essentialistic theory of dispositions as an alternative to Prior's. The theory claims that there exist ungrounded (bare) dispositions. According to the theory, the ungrounded dispositions are identical with their causal bases, and are causally potent for that reason. It is also claimed that dispositions are intrinsic and actual properties of their bearers.