Some philosophers object that non-reductive physicalism does not in fact satisfy the original motivation for physicalism, on the grounds that it does not really reconcile the efficacy of mental and other special causes with the causal closure thesis (Kim 1998, Robb and Heil 2014: Section 6). According to non-reductive physicalism, special properties are not type-identical with any strictly physical properties, even though they supervene on them. And this then seems to imply that any given special cause will be distinct from the physical cause that realizes it, since it involves the instantiation of a different property. (The property of thinking about the square root of two is definitely a different property from the neural property that realizes it in me, say, since another being could share the former property without sharing the latter.)