Gabriel Segal

The paper begins with the assumption that psychological event tokens are identical to or constituted from physical events. It then articulates a familiar apparent problem concerning the causal role of psychological properties. If they do not reduce to physical properties, then either they must be epiphenomenal or any effects they cause must also be caused by physical properties, and hence be overdetermined. It then argues that both epiphenomenalism and over‐determinationism are prima facie perfectly reasonable and relatively unproblematic views. The paper proceeds to argue against Kim’s (Kim, 2000, 2005) attempt to articulate a plausible version of reductionism. It is then argued that psychological properties, along with paradigmatically causally efficacious macro‐properties, such as toughness, are causally inefficacious in respect of their possessor’s typical effects, because they are insufficiently distinct from those effects. It is finally suggested that the distinction between epiphenomenalism and overdeterminationism may be more terminological than real.

A good understanding of the nature of a property requires knowing whether that property is relational or intrinsic. Gabriel Segal's concern is whether certain psychological properties—specifically, those that make up what might be called the "cognitive content" of psychological states—are relational or intrinsic. He claims that content supervenes on microstructure, that is, if two beings are identical with respect to their microstructural properties, then they must be identical with respect to their cognitive contents. Segal's thesis, a version of internalism, is that being in a state with a specific cognitive content does not essentially involve standing in any real relation to anything external. He uses the fact that content locally supervenes on microstructure to argue for the intrinsicness of content. Cognitive content is fully determined by intrinsic, microstructural properties: duplicate a subject in respect to those properties and you duplicate their cognitive contents. The book, written in a clear, engaging style, contains four chapters. The first two argue against the two leading externalist theories. Chapter 3 rejects popular theories that endorse two kinds of content: "narrow" content, which is locally supervenient, and "broad" content, which is not. Chapter 4 defends a radical alternative version of internalism, arguing that narrow content is a variety of ordinary representation, that is, that narrow content is all there is to content. In defending internalism, Segal does not claim to defend a general philosophical theory of content. At this stage, he suggests, it should suffice to cast reasonable doubt on externalism, to motivate internalism, and to provide reasons to believe that good psychology is, or could be, internalist.

Allow me to recapitulate some territory that will be familiar to most readers. Here is how the problem of mental causation has typically been set up since shortly after the onset of non-reductive physicalism. It is now widely assumed that the realm of the physical is causally closed: every physical event has a complete physical cause, a cause that is sufficient for the event’s occurrence. This apparently leaves us with a limited number of options concerning psychological causation, none of which appear hugely attractive. Either: (a) the psychological is epiphenomenal and can have no causal impact on the physical, or (b) the psychological is identical with the physical, or (c) thoughts and actions are all over-determined, each one having two distinct sufficient causes. Option (b) subdivides into two further options. Either (b1) the psychological reduces to the physical and every psychological property is identical with some physical property, or (b2) token psychological events are identical with or constituted from token physical events but psychological properties are not identical with physical properties. (b1) is widely held to be inconsistent with the multiple realisation of the psychological by the physical. And (b2) appears to bring us back to the original problematic, with the properties as the locus of tension. If one event causes another it does so in virtue some of its properties and not others. If I throw a stone at a window and the window breaks, it is because the stone was hard and heavy that it broke the window and not, say, because it was grey and millions of years old. The properties in virtue of which an event has a particular effect are typically called the ‘causally efficacious properties of the cause with respect to the effect.’ Suppose, then that token neural event causes an action. We can ask ‘Does it do so in virtue of its physical properties or its psychological properties?’ and we are back to choosing between options (a) and (c) or returning to (b1)..