A variety of recent philosophical discussions, particularly on topics relating to complexity, have begun to reemploy the concept of ‘emergence’. Although multiple concepts of ‘emergence’ are available, little effort has been made to systematically distinguish them. In this paper, I provide a taxonomy of higher-order properties that (inter alia) distinguishes three classes of emergent properties: (1) ontologically basic properties of complex entities, such as the mythical vital properties, (2) fully configurational properties, such as mental properties as they are conceived of by functionalists and computationalists, and (3) highly configurational/holistic properties, such as the higher-level patterns characteristic of complex dynamical systems. Or more simply: emergence as ontological liberality, emergence as multiple realizability, and emergence as interactive complexity.

Antireductionist philosophers have argued for higher-order classi cations of qualia that locate consciousness outside the scope of conventional scienti c explanations, viz., by classifying qualia as intrinsic, basic, or subjective properties, antireductionists distinguish qualia from extrinsic, complex, and objective properties, and thereby distinguish conscious mental states from the possible explananda of functionalist or physicalist explanations. I argue that, in important respects, qualia are intrinsic, basic, and subjective properties of conscious mental states, and that, contrary to antireductionists' suggestions, these higher-order classi cations are compatible with qualia reduction. I demonstrate this compatibility by examining the putative higher-order properties of qualia and comparing them to the higher-order properties characteristic of connectionist models of cognitive processes. I contend that the higher-order properties characteristic of connectionist networks approximate (in intertheoretic terms) the putative higher-order properties of qualia suf ciently well to conclude that qualia reductionism can (1) accommodate claims that qualia are intrinsic, basic, and subjective properties, and (2) explain the motivating intuitions for those claims generated by inverted, absent, and alien qualia thought experiments. In this way I argue that (approximate versions of) the putative higher-order classi cations of qualia not only fail to defeat qualia reduction but, ironically, turn out to support it.

Hugo Mercier and Dan Sperber, The Enigma of Reason (Cambridge, MA: Harvard University Press, 2017). 396 pp. $29.95 (hbk). ISBN: 978-0-67436-830-9.

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