Philosophy of Mind
Introduction Dualism Behaviourism Identity Theory Functionalism Dennett

Identity Theory:
 
 
 
  Identity Theory and Dualism
 
  Some Problems:
 
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Reading My Brain
 
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Type-Type
 
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Type-Token and Token-Token
 
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Multiple Realisability
  Summary
  Further Reading


  Type-Type 
 

We may throw light on these problems by distinguishing between the different sorts of identity. For instance, we may call a certain class of objects – such as cars - a “type”, whilst a particular car – a Fiat Punto – may be called a “token”, or representative of that type.

Now, some forms of Identity Theory argue that certain types of brain state are identical with certain types of mental state. So, all sorts of happy mental states would be identical with certain sorts of brain states. This is known as Type Identity Theory.

This form of the theory assumes two things:
  • Everytime you are in a certain mood – such as being happy – there is the same corresponding brain state
  • The same mood/brain state relationship occurs in everyone else

There are numerous problems with this view. First of all, can we really say that all my happy moods have something in common? If I write down the defining characteristics of all my different moods, won’t I find that some very different moods have a lot in common (fear and excitement, for instance)? So, doesn’t this suggest that – even if brain states are mental states – all happy states might correspond to a range of very different brain states?

The next problem concerns how we can be sure that the same mental states produce the same brain states in other people. Suppose that I am conducting an experiment to find out exactly what your brain is doing when you are in a certain mental state. I do this by asking you to think about certain things or perform certain mental activities. Every time you do something, I can see parts of your brain become active, suggesting that that part of the brain is responsible for doing that thing. Now, suppose I do this experiment for other people using the same activities and their brain behaves differently. Do I then assume that they have not carried out the activity properly? They are mistaken? They are lying. This is commonly known as the benchmark problem and is responsible for a refinement of the theory known as Token Identity Theory.