The multiple realization book

In this review of Thomas W. Polger and Lawrence A. Shapiro’s The Multiple Realization Book I look at the positive account, Modest Identity Theory, that Polger and Shapiro advance. In §2 of this review, I outline P&S’s arguments against multiple realization and summarize the view they defend, Modest Identity Theory. In §3, I consider what consequences the adoption of Modest Identity Theory might have on the ontology of psychological or mental kinds. In particular, I highlight the ontological pluralism and anti-reductionism that Polger and Shapiro endorse. Modest Identity Theory tolerates multiple taxonomies of psychological kinds, which represents an important departure from earlier versions of Identity Theory. I conclude in §4 by arguing that the way Modest Identity Theory individuates psychological kinds very closely resembles the way that those kinds are individuated by functionalism. I argue that the causal properties individuative of psychological kinds can be used to group together distinct neuroanatomical characteristics. I illustrate this by describing research into the functional connectivity of the reading network. I conclude by emphasizing the value of using empirical evidence from neuroscience and cognitive science to inform the new pluralistic ontology of psychological and mental kinds with which Modest Identity Theory is compatible.