This collection is a valuable addition to the literature on the metaphysics of the mind as it collects together some of the major writings of a key figure in current debates. One will not find a realist conception of the mind and a fairly no-nonsense variety of physicalism more thoroughly set out for discussion and critique. Kim eloquently and insistently outlines the case for a functional reduction of mental properties and the mind. For Kim, such things as ‘the activation of a group of neurons …. As the state typically caused by tissue damage and that in turn triggers aversive behaviour’ (74) are the categorical basis of mental states and events.
The reductive identity thesis is linked to the claim that the causal powers of the neural realizer are the causal powers of the mental state concerned. Taken together with the argument that a cause – the nomologically sufficient condition to produce an effect – must be a physical state, this view secures Kim's conclusion that mental life is at base a string of neural events connected in the way they are because of causal connections between them and explicable in those terms.
He uses this metaphysical view to undermine a coherent concept of emergence as the basis of significant explanatory properties and relations operating in the lives of human beings (‘the why of it’). Explanatory knowledge is, he argues, based on the ‘objective causal relation … holding outside our epistemic system’ (172) so that the real knowledge underpinning explanation incorporates a kind of externalism – a body of thought responsive to what is actually at work in the world rather than just a set of beliefs, systems of concepts, constructions of reality and modes of explanatory connection. This is down home causal explanatory realism and it trades, inter alia, in the mereological dependence of facts on fundamental states of affairs that exist in the actual world. Dependence of the sort Kim wants is asymmetric and transitive and ultimately grounded in the physical structure of this world: ‘every ostensibly non-physical phenomenon can be reductively explained in terms of physical phenomena’ (211). Thus the explanatory value of mental properties, for Kim, depends on the causal powers of their physical realizers. In this and nearby worlds, physical states are the truly explanatory underpinnings of our mental lives in virtue of the physical kinds they instance and the causal powers of those physical kinds.
So much for the theory, now for some quibbles.
First, there is a kind of pervasive naivety in the essays best illustrated by two claims:
1. ‘genes have been reduced – functionally reduced – to DNA molecules’ (222); and
2. at the fundamental physical level something like causation operates (251).
Kim actually fudges the second point but it is crucial. If the model of causation he has does not have currency at the most fundamental level of physical description then its claims to be the ground, in the real world, on which explanation is built throughout science starts to look shaky. In fact we find that a set of competing descriptions, in a literal sense (i.e. according to the pictures we form when we take things literally), that are incompatible with one another have equally compelling claims to truth at the fundamental level. But if that is so when we are trying to investigate the building blocks of all our ontology, then it is odd that it is not true when we get to the level of neural function and mental function. But even there mechanistic causality is definitely not a good model of reality and we should be thinking about vectors, fluxes of neural excitation, mathematically steady states and the emergent regularities of chaos theory. Kim's ontology is, therefore, yet another metaphysical fiction applicable to middle sized dry goods of which our neural nets not an instance.
The ontological problem comes home to roost in the genes claim. Genes have not been reduced to DNA molecules. Genes, thought of as the actual basis of genetically heritable traits, are complex interactive nexes of nucleic acid molecules, epigenetic and tissue factors, and ecological niches that result in the expression of phenotypic variations. And here there is a direct analogy with mental realities.
Aristotle not only drew our attention to ‘they why of it’ but also remarked: ‘the soul is to the body as sight to the eye’ (De Anima). His remark bears further attention.
The physical basis of sight in animals is, in part, the eye but one can become fixated on retinal layers, pigments, mechanisms of photo-excitation, topography and so on and forget that, in fact, sight is primarily a method of teleoception using patterns in the light that convey information about the environment. As such it uses brain systems and connections to which the eye is just the entry point. Without that knowledge of the real nature of sight, we cannot make a lot of sense of the intricate anatomy and physiology of the encapsulated organic jelly ball that is an eye. In the same way, the ecological context within which we understand a human brain and what it does is one in which people relate to each other discursively and use discourse to shape their adaptation to their world. Discourse is massively structured by signs and intentionality (involving reference and sense). The brain relates the normatively governed semantic activity and the biological context of ecological adaptation so that the world in which we become equipped with minds is the human life-world and the way we relate to it is shaped by our structures of meaning.
One can infer from that fact about our ethology that sometimes the cause of a state in a human being can only be explained by appealing to entities that are metaphysically part of the discursive world rather than properties identifiable within a physical model of the world. Consider the following. Human being X receives a lamellated piece of cellulose based material with pigment on it. Within the myocardium of X there occur physiological changes that disrupt its metabolism perhaps to the point of cell sickness and death. A physically oriented scientist is equipped to detect poisons and other active chemicals that may have affected X's biology. However that approach, based in physical science is fruitless. The fact is that she received a letter telling her that her husband had just been killed doing search and rescue work in an earthquake zone. She has ‘broken heart syndrome’ – an event like a heart attack induced by sudden grief or loss. To explain this we need to invoke a number of things about human beings that are not part of our neuroscientific understanding, including the language the letter is written in, the nature of the husband-wife relationship, and so on. Only a human understanding of these things can explain why she has felt what she felt and reacted as she did. Similar examples are the hysteria following a radio programme in which ‘The war of the worlds’ is dramatised in a certain way or a whole range of historical events that neuroscience just does not have the conceptual equipment to engage with. These things involve connections between mind, meaning, and reactive attitudes, that are not dreamt of in Kim's explanatory ontology.
There is also a troubling naivety that we might call the belief in vertical fidelity in metaphysics. The thought is that an explanatory type in the world of mind or meaning is going to have a detectable echo in the projectible or individuated types of neuro-science. But the mental type associated with boojum is not likely to correspond with any principled grouping of states surveyable at the neural level. The only way to identify the relevant set of such states is to map uses of the term boojum onto tracts of brain imaging in some way and the neural set generated is unlikely to have principled individuating criteria to make it an instance of any identifiable neuroscientific type. What is more if, having delineated a set of states, a new subject did not have a neural state fitting the parameters (which are, as argued, probably unspecifiable) but who did understand the use of boojum, then the mental ascription is authoritative and the brain-based specification of the state has to be modified. Therefore the individuating conditions of the set of brain states seen as realizers depend on a term defined in a nexus of mental connections rather than on anything generated by neuroscience.
Kim wisely skirts the issues of top down causation (or upward metaphysical dependence) but it seems there are three senses in which top-down explanations might be indispensible to us. First, they might be indispensible in making sense of what is going on at a physical level (as in the case of a broken heart). Second they might be indispensible in identifying the entity (should there be one) that counts as a physical or brain state of a given type (the physical realizers of understanding boojum for instance). Third, the states that a brain gets into may only be explicable on the basis of the history of that brain as the brain of a person located in the human life world at a certain point such that certain adaptations have shaped its neural networks – learning Swahili, then being removed to New York, then being trained as a microsoft graphics designer for ‘Sim’ games, and so on. But if neural or brain states are, in principle, often only explicable by appealing to such things as meaningful human relationships and being exposed to cultural icons (such as ‘the Hunting of the Snark’) and if causation is a reflection and articulation of the metaphysical dependence of a state of affairs on those that explain it then Kim's metaphysics of mind embeds a serious mistake.
The saying, ‘Keep your friends close and your enemies closer’ has some application to philosophy. Kim's metaphysics is supposedly part of this or a nearby world but it is not near enough; his reliance on a subvenient level of neural entities corresponding to mental states is not compatible with our understanding of this world where such things do not exist (either in type or token form) so that belief in them is a matter of misbegotten faith.
