This essay assesses mind-brain identity, a material monist theory of mind most associated with Donald Davidson. The central tenant of the theory is that mental states are identical with, but not reducible to brain states. The two descriptions are both valid in their own right, but describe the same thing.

This question asks us to discuss an idea that is central to the mind/brain identity theory of mind. However before we examine this we must first be aware that the question itself assumes that there are such things as mental states. Thus we cannot answer this question from the standpoint of some theories (two examples being eliminativism and functionalism).

Donald Davidson is most associated with the identity theory of the mind. Identity theory is a materialist position in that it asserts that everything is physical. Thus, although it speaks of mental states it does not assert (like Descartes) that these are not physical.

The central tenant of the theory is that mental states are identical with, but not reducible to brain states. The two descriptions are both valid in their own right, but describe the same thing.

This can be seen in the type-token distinction. A type is a classification or a class, whereas a token is a member of that class. In this case Davidson asserts that there is no distinction between the type of thing (both mental and brain states are physical), but instead that descriptions of mental states and brain states are tokens of the same type. By way of illustration, consider a type (i.e. classification) of philosophers. You and I might both belong to this type, and thus in a sense be identical on this parameter, but we are also obviously different and can be enumerated separately (i.e. we are different tokens of this type)

Davidson developed a further exploration of this argument in his concept of Anomalous Monism. As before the descriptions of mental states and physical states are seen as both valid in their own right. Also it is asserted again that the same underlying thing is described. The key point for anomalous monism is that the two descriptions describe the thing in such a way that they cannot be phrased in terms of each other.

Davidson uses the example of lightening. We could describe lightening in terms of a bright flash and load noise. However we could also describe the same event as a discharge of electromagnetic energy from the atmosphere to the earth. The same event is being described in both cases and both descriptions are valid. Crucially the two explanations are not reducible. It is not possible to construe one description in terms of the other.

To highlight this difference, notice that one description (flash and noise) is essentially experiential and the other (electromagnetic energy) is purely neutral. We could describe the event of going to a concert in terms of the wonderful song we heard, or we could describe it in terms of a voice being amplified and emitted as vibrations from a speaker. Both describe the same event, but both fail to capture the whole; the physical description fails to capture the experience and the mental description makes generalisations about what is happening.

Thus, states identity theory, whilst we can analyse what a physical description is and analyse what a mental description is we cannot analyse the relationship between the two, as there is none.

All of this work on identity theory can be part ascribed to a need to respond to functionalism and the computational accounts of mind that were prevalent at the time. However, even more than this Davidson wanted to avoid reductionism. Materialist theories of mind are associated with a reduction of the mental to the physical. Davidson saw that descriptions of consciousness and mental states were fundamentally different to descriptions of physical states, but did not believe that they were two different substances (as in Cartesian dualism).

Davidson could be accused of simply trying to get the benefits of dualism and materialism whilst avoiding their criticisms, but he is apparently most concerned with preserving the notion of consciousness whilst retaining a materialist stance.

In support of the theory it can be said that the theory is intuitively more appealing than reductionist or eliminativist theories. It seems more reasonable to suggest that how we describe our mental states might be valid rather than to reduce these to physical states or to deny that they exist altogether.

Furthermore, if the theory is indeed correct, Davidson has managed to accommodate both those materialists that adhere to computational accounts of mind and those people who wish to preserve the notion of consciousness. By logically showing that the two accounts are not reducible, but are equally valid he has potentially appeased both sides.

It seems that there is much in human experience that cannot be couched in purely physical terms, and the fact that identity theory acknowledges this is a significant benefit. Take for example a meeting. A physical description might be 'a meeting is a proximate collection of organisms of the same species causing the air to vibrate whilst some electrochemical processes occur within their brains'. Whilst this might be an adequate generic description of all meetings it fails to capture the essence of the situation. For example the same physical description could be applied to the founding fathers agreeing the constitution of the United States and also to the finance department of Townsville borough council agreeing a seating plan for their forthcoming Christmas meal. Fairly obviously the physical description fails in some fundamental way to record the experience of the meeting. However, in the same way a purely mental description (e.g. 'this is an historic gathering of great minds for the betterment of mankind') might fail to capture all of the events (i.e. where it took place, who was there, what happened, etc). Identity theory allows for these very different descriptions without the need for recourse to dualism.

As with all theories, identity theory also has its detractors. One argument against the theory centres on the logical implications of identity. According to Leibniz, if two things are identical then anything that can be said of one can be said of the other - they will be identical in every property and because of this reducible to each other. Thus, to counter identity theory it can be argued that to posit that mental states and brain states are identical and then describe one of them as not reducible to the other is logically impossible.

Davidson though, had foreseen this criticism and had prepared a counter example. Suppose that two people have sunburn he suggested. One sat in the sun for too long and the other under a sun lamp for too long. The physical condition of the two people is the same in every respect, thus conforming to the Leibniz doctrine, but nevertheless there is a crucial difference in the cause of that condition says Davidson. This shows that there can be two identical states that can be described differently.

A potentially more damaging attack on identity theory is that it is simply attempting to appease everyone (i.e. materialists and those wishing to preserve consciousness) and that as a result the theory is not a coherent whole in its own right. It could be construed that Davidson has tried to gain the benefits of dualism and materialism whilst losing the objections to both. By retaining consciousness (as in dualism) and a purely physical existence (as in materialism) perhaps he had produced a theory that is not internally consistent, or at the very least may inherit the refutations of both types of theory.

A further issue arises with privacy. Surely mental descriptions would have the benefit of first person perspective over physical descriptions? Firstly, this could be used as another attack on the theory using Leibniz's law. Secondly, this implies that mental states have a relationship with physical states. Identity theory rests on the idea that descriptions of mental and physical states derive from the same single, physical event, but that there is no relationship between these descriptions and that thus they are not reducible to each other. So how is this relationship implied? If I have exclusive and infallible access to my internal state then it must follow that if I report a pain (i.e. provide a description of a mental state) that physical examination of will confirm that I am experiencing a pain (i.e. that the mental and physical descriptions match in describing a single physical event). For the physical examination to contradict my report of pain would be very problematic for identity theory. J.J.C. Smart answered this in 1962 by simply pointing out that this would never occur, which seems ad hoc. In addition, if this really were never to occur it would also seem odd that there is no relationship to enforce that state of affairs. This issue thus brings others into play, namely those of psychophysical causation and infallibility of access to one's own internal states.

A further attack arises from this discussion of the necessity of there being no relationship between descriptions of mental and physical states. How is it possible that the descriptions are identical to one another without the identity being a relationship in itself? At the very least it would seem that the meaning of the word identity is being stretched to accommodate this assertion.

The final consideration arises from the issue of multiple realisability. Type identity theory encountered problems because it specified that mental states were exactly alike (and thus theoretically reducible to) physical states. This meant that each mental state must have precisely the same physical embodiment in every instance. However, it is quite plausible that different physical states might give rise to similar or even identical mental states. This seems especially plausible when one considers not just the differences between individuals, but the mental states of other species.

Davidson's version of identity theory type (the token-token version) however avoids this issue because the two tokens (descriptions of mental states and physical states) are of the same type and are not reducible to each other, thus allowing for multiple realisations. Thus, a description of more than one physical state can be identical with a description of a single mental state. For example, suppose that you describe feeling ambivalent. There must be a range of differing neural interactions that could lead to this feeling. This can also be shown to be true when considering the plasticity of the brain, e.g. the way in which an area of the brain can alter to take on a function performed by a damaged area. If I had had a stroke and re-learned to walk, then I might be able to describe the same mental state of the experience of walking as you whilst we both have different physical processes occurring in our brains.

At this point a further distinction must be made. Take the example of Superman and Clark Kent. We know that they are the same person, but to say Superman = Clark Kent is not true a priori or in an analytic sense. It is only true by virtue of experience, or de re, a necessity as a property of the world, it would not be true de dicto, necessity as a property of language (like a triangle has three sides). This means that in our experience the name Superman identifies a person and the name Clark Kent identifies the same person. However, although in all possible circumstances these names will refer to the same individual it is possible that another individual might also have the name Clark Kent. Thus, under these circumstances the statement Superman = Clark Kent might not be true.

In the case of identity theory the fact that a mental description is associated with a physical description is dependent on circumstances. To say that descriptions of mental states are identical to descriptions of physical states is never true in an analytic way and could logically even be incorrect in certain circumstances. Considering multiple realisability in the light of this we can see that physical state 'A' might be identical to a number of different mental states or vice versa and that they might not be identical in all possible circumstances.

If this were the case it would mean that even if my description of a mental state is identical with your description, our physical states might not be identical. If this is the case in what way are our experiences rendered public by identity theory? Physical examination cannot thus be shown to lay bare internal experience, which leaves the theory open to charges that it is solipsistic.

Thus, in conclusion to this critical discussion of the idea that mental states are identical to physical states it seems that we can agree with the principle that the descriptions of the two states can describe the same event in a way that is not reducible. However, the theory does not appear to provide a conclusive case either that consciousness is a purely physical phenomenon nor a consistent statement of how mental states are identical to physical states.

1. The internet encyclopedia of philosophy entry for identity theory by Steven Schneider
2. www.dictionary.com

Tutor: Oliver McAdoo MA

WWW www.arrod.co.uk