Examining each account, which, if any, of the following accounts of the mind/body relationship is the most convincing? Dualism, Identity Theory, Functionalism, Eliminative Materialism, Philosophical Behaviourism

Although it seems clear enough what we mean when we think of ourselves as possessing a body, what is the thing that we refer to as the mind? Whereas the body is tangible, visible and externally verifiable, the mind is highly personal, internal and unseen. That we do have a mind is almost certain, where it is located and in what form will be explored in the following. With reference to the two main competing theories of mind, Dualism and Monism, I hope to sketch out which is the most convincing theory based on the evidence we currently have at our disposal.
Dualism has had two main historical iterations; the first arose in Plato’s Phaedo (1993) where the philosopher argued that true substances are not physical bodies but imperfect copies of the eternal Forms. The idea is a useful one, insofar as the Forms render the world intelligible in terms of what Frege called ‘concepts’ (2003) i.e., because, Forms are the grounds of intelligibility; they are the intellect must grasp in the process of understanding. The second iteration and modern origin of dualism was expounded by Descartes in his Medidtations (1996)and is the starting point of the contemporary mind/body discussion. Dualism is the theory that the mental and the physical, or the mind and the body, are in some sense profoundly different kinds of things. Because we intuitively realise that there are physical bodies, and because there is an intellectual pressure towards unifying our view of the world, one could say that materialist monism is the default option. Our discussion of dualism, therefore, will begin with the assumption of the reality of the physical world, and then consider why the mind might be considered simply as a part of that world.
Dualism exists in three main kinds, property dualism, substance dualism and predicate dualism. Predicate dualism is the theory that psychological predicates (such as ‘this apple is red’ where red is the experience of seeing red) are i) essential for a complete description of the world and ii) not reducible to physicalistic predicates (such as ‘this apple is red’ where red refers to electromagnetic radiation with a wavelength of approximately 680 nm). For the mental predicate to be reducible there would have to be a connection between types of psychological states to types of physical ones such that the use of a mental predicate carried no more information than the use of a physical one. An example of such a true type reduction is well explained by considering the case of water. Something is water if and only if it is H2O. It is safe to assume that in most cases if we say H2O instead of water we will convey the same information. However, there are many things that are not susceptible to such a true type reduction. Not every election, pop concert or infectious disease has the same constitutive structure. Indeed, these things are more readily defined by what they do rather than by their composition or structure and they are consequently classified as functional terms rather than natural kind terms. A character of these kinds of states is that they are multiply realisable i.e. they may be constituted by different kinds of physical structures under different circumstances. Because of this, an unlike our example of water given above, we cannot replace the term ‘infectious disease’ with some basic physical description and hope to convey the same information. Because mental states are widely agreed to be similarly irreducible, psychological predicates are not reducible to physical descriptions and we are left with predicate dualism.
Predicate dualism is essentially an assertion that there are two different kinds of predicates in our language. Property dualism says that there are two fundamentally different types of property in the world. Although the predicate ‘hurricane’ is not equivalent to any single description using the language of physics, it does consist of the same physical conflation of atoms, following normal physical laws, in every occurrence of a hurricane. There is a token identity shared by each hurricane and a mass of atoms, even if there is no type identity between hurricanes as kinds and some structure of atoms as a kind. Property dualism is found where the ontology of physics is insufficient to constitute what is there and it is defended by those who argue that the qualia of the conscious experience is not just another way of categorising states of the brain, but a genuinely emergent phenomenon.
So where Property Dualism is an assertion of the emergent properties of the brain, substance dualism asserts that there are two discrete types of substance that make up our conscious experience. Usually, a substance is characterised by its properties. According to the substance dualist, a substance is more than just the sum of its properties but it is the thing which possesses them. In the case of the mind, it is more than just a collection of thoughts; it is the thing that thinks them too; an immaterial substance which is responsible for producing the immaterial mental states.
There are, of course, problems with some elements of the dualist perspective namely, interactionism and epiphenomenalism and are discussed below.
If the mind and body are separate entities, how do they interact? Most would agree that there is some kind of causal interaction: thinking about food tends to lead to an attempt to acquire it (the mental influencing the physical) and burning one’s finger on the stove tends to lead to increased caution when cooking (the physical influencing the mental). However, this interaction appears to violate some basic principles of physical science, namely, the conservation of energy within a physical system. If causal power were flowing in and out of physical system, energy would not be conserved. Although quantum theory may eventually show that the physical laws are not deterministic and that interaction between mind and body may preserve a kind of nomological closure, such speculation is beyond the scope of this paper.
Some philosophers deny that there is a flow of interaction from the mental to the physical; this view is known as epiphenomenalism. Mental events may be caused by physical events, but have no causal influence on the physical. Although this theory is attractive to those who wish to preserve the autonomy of the physical, it encounters two serious problems. The first problem is that it is profoundly counter-intuitive: it is; it seems, so obvious that hearing a funny joke makes me laugh or that my fear of snakes prevents a trip to the zoo that to deny the causal influence of the mental on the physical seems plainly wrong. The second problem has an evolutionary basis and is simply the observation that if mental states do nothing then they ought not to have evolved. This is linked to the first intuition insofar as a fear reaction to a snake clearly influences our behaviour in a way that is evolutionarily beneficial.
Another problem for dualism is the apparent intentionality and subjectiveness of the cognitive experience. Mental states are composed of two main characteristics, privileged access and intentionality. Physical objects are sometimes observable, such as the car on the street and sometimes not, like the electron, which must be detected using special instruments. However, all physical objects are equally accessible, in principle, to anyone. The possessor of a mental state, though, has a privileged access to them that is inaccessible to everybody but herself. This is what gives rise to the skeptics problem with other minds, although there is no corresponding problem with my own mind e.g. I know that shirt is red, and my friend tells me that he also sees the shirt as red, but how do I know that his experience of red is the same as my own?
Physical objects are spatio-temporal and have spatio-temporal causal relations. Mental states have causal powers but they are also intentional i.e. they are about other things, including things which do not actually exist like unicorns and the square root of minus one. No physical thing could be said to be about something else. The nature of the mental is both queer and elusive. Ryle (1949) says that the mind, as adumbrated by the dualist, is a ‘ghost in the machine’: something mysterious and unintelligible trapped inside something mechanistic and intelligible.
The Monists response to the mind/body problem is to assert that there is no duality, that the two are not distinct after all. The most common monist perspective is that of physicalism. Put simply, the physicalist believes that everything in the world is physical, including some things which seem intuitively non-physical such as oration and morality. Physicalism is the modern incarnation of materialism. Materialism was historically concerned with the notion that everything was matter and that matter was considered “an inert, senseless substance, in which extension, figure and motion do actually subsist” (Berkeley, 1710). The idea is now referred to as physicalism to reflect the fact that some things, such as the force of gravity, are physical but not apparently material in the historical sense.
Although physicalism is a metaphysical notion, it is closely allied to the scientific discipline physics. It is clear that physicalism is both monist and that it provides a way to approach the mind/body problem: if everything is physical, then it is probably in physical theories that we will find answers. There are several forms of physicalism that approach this problem in different ways. The main ones that I shall discuss are supervenience, type and token physicalism.
Supervenience physicalism is best illuminated with an example. If we consider the output of a computer monitor or television screen we realise that the picture consists of thousands of small points of colour, yet the global properties of this collection of dots is the picture on the screen. The picture supervenes on the dots. So, the basic idea of physicalism is that the physical features of the world are like the dots in the picture, and the psychological or social features of the world are like the global properties of the pictures. Just as the global features of the picture supervene on the dots, so too everything supervenes on the physical. Furthermore, no two possible worlds can have identical physical properties and different supervenient ones.
Type physicalism (sometimes known as identity theory) argues that mental states correspond identically to internal states in the brain, so mental state M is identical to brain state B. The mental state of lust ‘that girl is very pretty’ is nothing more than ‘activity of particular neurons in particular regions of the brain’. Despite its intuitive plausibility, physicalism type is strongly challenged by multiple realisability which challenges the empirical foundation on which it is based. An example of this is as follows; it seems obvious that animals such as other mammals feel pain; however, as the brains of other mammals are not identical to our own, it seems unfounded to assume that pain has an attendant specific brain state to which it corresponds. Token identity theorists manage to sidestep this impasse by arguing that type theory is too rigid and that the fact that a certain brain state is connected to a certain mental state does not mean that there is an absolute correlation between types of mental states and types of brain state. This distinction between type and token can be illustrated by the following example: The word green contains four types of letters (g, r, e, n) along with two tokens of the letter e and one each of the others. Token physicalism is the idea that only particular occurrences of mental events are identical with particular occurrences or tokenings of physical events.
Functionalism concerns itself with the question of what does the mind do rather than what kind of thing it is. It is an attempt to distinguish it from the body by saying that its functions are different to the bodily functions. Consider a door. A door may be twenty feet tall, a foot thick and be blocking the entrance to a castle, or it may be made from MDF and blocking the entrance to your bathroom. At any rate, in both cases the object described is a door. That is its common function. According to functionalism we can consider mental states in the same way, as being defined by their functions, and avoid the problems of physicalism by not having to worry about what a mental state is like. The problem with this perspective is that there is an explanatory paucity when it comes to dealing with qualia. The causal nature of the descriptions that functionalists use to explain mental states are insufficient to describe the qualitative character of experiential states such as perceptions and emotions, since they would necessarily leave out their essential properties, or ‘what it is like’ (Nagel 1975) to have them. The inverted qualia example illustrates this: a person could exist who satisfies the functional definition of our experience of red, but who is actually experiencing green instead.
Eliminative materialists’ claim that our common-sense understanding of mental states is essentially wrong and that some or all of our ordinary notions of mental states will have no place in any level of analysis in a modern and accurate account of the mind. It is the view that certain common-sense mental states, such as beliefs and desires do not actually exist. To establish this, eliminative materialists posit that folk psychology is totally wrong about the actual nature of the mind and that the central tenets of folk psychology radically misdescribe cognitive processes. Consequently, folk psychologists identify nothing that is actually real. Like dualists, eliminative materialists insist that mental states are irreducible, but unlike dualists, they hold that there is nothing more to the mind than what happens in the brain. The reason mental states are irreducible is not because they are non-physical, but because they do not exist as described by common-sense psychology.
For example, our notion of demonic possession did not find a home within the explanatory framework of modern theories of mental disorder; rather, they were jettisoned as we gradually accrued more knowledge about the nature of conditions such as schizophrenia and Tourette’s syndrome. The notion of demons is so far removed from the theories we now use to explain behaviour that would, in the past, have been blamed on possession it can only be described as a radical ontological shift. Eliminative materialists claim that an ontologically radical theory change of this kind awaits the theoretical posits of folk psychology. Just as we come to understand that there are no such things as demons, so too will we come to realise that various folk psychological concepts, such as out notion of belief, are empty posits that do not correspond with anything that actually exists.
A problem with eliminative materialism is that it can be seen in some sense as self-refuting. A common way this charge is made is by the critic insisting that in making their assertions, the eliminative materialist must hold a belief that is the subject of their assertions. But if the eliminativist holds such a belief then there are beliefs and eliminativism is proven false. A common response to this objection is that this sort of claim about beliefs is exactly the sort of folk-psychological assumption that the eliminative materialist is suggesting we should abandon, and that this sort of self-refutation merely begs the question.
Given all of the above, I see the biggest problem for monism as the problem of how it deals with qualia. This is most readily expressed using the knowledge argument. One form of this argument runs thus: John is a scientist. For some reason he has spent his life trapped in a room in which the only colours are black and white. He can watch television and use computers but the screens are all in black and white. Consequently, he has never experienced colour. He is able to access all the information he can via the Internet so he knows about how the eye works, what light is and what happens when it hits the retina. He knows what it means to say that ‘the grass is green’ and he has all the possible information that such a statement concerns. One day, John is released from his room and actually sees the grass outside and he learns something new, namely that qualia, or what-it-is-like-ness to experience colour. So, John had all the information about colour before he left his room and learned something new about it after experiencing the colour for himself. So it seems that there is something non-physical about information. This presents the strongest challenge to monism.
As far as Dualism is concerned, the biggest problem for this set of theories appears to be the explanatory gap between what we know about the physical world and what it is like to have an experience. Underlying this is the very real problem of pinning down the link between the material and the immaterial sides of the mind/body duality. I suspect that as neuroscience advances and we gain a more complete understanding of exactly how the brain works some of the more intractable problems of this debate will become more malleable. Until that becomes a reality. I remain convinced that the weak predicate form of dualism is the best tool we have to explain and understand our conscious experience. This is because it is the one most closely related to materialism in the sense that it does not posit an immaterial substance that we may never be able to detect and it seeks to reduce the problem of the duality of mind and body to a linguistic, rather than materialistic dualism. This view is attractive because, unlike property and substance dualism, it allies most neatly with an intuitively materialistic global ontology. Also, it sits well with the problem of multiple realisability and does not require one to make any counter-intuitive concessions in order to maintain one’s position.