3.4.4 Mind-Brain Type Identity Theory

Occurs when one type of entity/being is shown to be the same as another type of entity or being in reality.

Different to an analytic reduction:

• Analytic reductions are concerned with meaning of concepts - e.g. behaviourism says that mental states mean behaviours

Ontological reductions are concerned with the nature of what exists - e.g. MBTIT says mental states are brain states.

Ontological theories talk about what words refer to not what words mean.

So ontological claims are synthetic claims about the nature of what exists (ontology).

A type is a category of thing, a token is an individual instance of that thing 

• e.g. a human is a type of thing, you are a token of that type 

• Pain is a type of mental state, the pain you’d feel if you pinched your arm is a token of that state

It claims that particular types of mental states are identical with particular types of brain state

• SO when Bob and Bill experience the mental state of wanting a cup of tea, they are both experiencing the same brain state

• Both their tokens of the mental state of wanting tea are tokens of the same type of brain state

So mental types of thing (mental properties, states and events) are physical types of thing (physical properties, states and events)

Tokens of mental states are identical with particular tokens of brain state 

• When bob and bill experience the mental state of wanting a cup of tea, they may both be experiencing different BRAIN states

• Both their tokens of the mental state of wanting tea correspond to a brain state, but not necessarily both to the same type 

• But their mental states still are identical to their own brain states

Neuroscience is constantly discovering more about the correlations between certain behaviours/mental states and physical occurrences in the brain. 

• For example, when certain parts of the brain become damaged certain mental abilities disappear. 

• When the visual cortex is damaged, the ability to see the colour red is affected. 

These sorts of discoveries confirm what we would expect to see if the mind-brain identity theory is true.

So science can show us a correlation between the mind and the brain.

This isn't a proof - it suffers from the problem of induction

Science can only ever show a correlation, not identity or causation 

So why argue that just because thoughts/feelings etc are correlated with brain states etc that they are the same?

If two competing hypothesis have equal explanatory power to explain the same one, we should choose the simpler one

Smart applies the principle of Ockham’s razor to the question of the nature of the mind

Simpler = fewest hypotheticals of unnecessary premises

If there are no overwhelming arguments in favour of dualism then we should reject the idea of distinct non-physical substances or properties

Science indicates that neurophysiological properties of the brain are a good candidate for what mental properties are

We can divide up the body but not the mind

So they are different 

P1: the body is divisible

P2: the mind is indivisible

P3: body and mind are not identical

C: therefore the body and the mind must be distinct substances

Therefore arguing against general physicalist ideas which includes MBTIT

P1: If I can clearly and distinctly recognise the natures of 2 things to be different, they must be distinct 

P2: I can conceive of the mind as a thinking thing

P3: I can conceive of the body as a non-thinking thing

C1: Therefore, I can clearly and distinctly recognise the natures of mind and body to be different

C2: Therefore they must be distinct

This criticises general physicalist ideas and so criticises MBTIT

Introspection reveals something different than when we look from the outside

e.g. Thoughts , sensations and emotions rather than electrochemical impulses

• If mental states really are physical occurrences why don't we experience them in the same way as we do all other physical occurrences

• If a thought really is a firing of neurons why don't we experience them as this?

• What accounts for this massive deceptions of our interior senses

Introspection reveals that we do not experience mental states as electrochemical impulse or strictly physical occurrences but as thoughts, sensations and emotions with qualia.

These subjective qualities of experience cannot be reduced to something physical.

However much we know about the brain, we still wouldn't know about qualia unless we explain them (knowledge argument) so it seems that the brain cannot be identical with the mind.

Its acknowledged that colour is purely a physical phenomenon.

Yet we don't consciously experience colour as different wavelengths of electromagnetic radiation.

So maybe mental states are - like colour - a physical phenomenon which we experience differently from what it is at the most fundamental level.

Certain criticisms have attacked MBTIT from the angle of the way we talk about the mind. 

We talk in a different way about the mind than we do about the brain. 

• When we say that we are in pain we don't mean that certain neurons are firing in the brain.

• If the mind and the brain were the same thing, surely we would talk about them in the same way, the concepts would mean the same. 

BUT

This criticism is easy to respond to, as it rests on a misunderstanding of mind-brain identity theory - MBTIT is claiming ontological identity NOT analytical identity.

• We don’t talk about water as if it is H₂O but it still is H₂O.

Similarly, it would say that talk about pain refers to certain neurons firing, not that it means certain neurons firing.

According to Leibniz's Law, if we can find a property of the mind that the brain does not possess, or a property of the brain that the mind does not possess, then we will have demonstrated that the mind cannot be the brain. 

The fact that brain states have a spatial location and yet that it seems to make no sense to speak of a mental state as having a spatial location, suggests the two cannot be identical. 

• e.g. it makes no sense to say a belief is 2 nanometres long.

We may not be used to speaking about our mental states in this way but when we learn the identities we may come to do so. 

MBTIT is an ontological theory and makes no claims about the concepts meaning the same, or being possible to us in the same way.

Intentionality is the quality of certain mental states which directs them beyond themselves and to things in the world.

Intentional mental states such as beliefs, desires and fears are about or represent something.

Intentionality is problematic for physicalists because it is unclear how this can be a property of any purely physical system.

• e.g. suppose three sticks fall from a tree and form themselves into the shape of an arrow. 

• Would the arrangement of sticks be pointing at anything? Can the sticks be about anything? Can they be directed or possess intentionality? 

• The reason we might say not is that there was no mind involved which intended them to be an arrow. 

• For some sticks to genuinely be pointing at anything they would need some mind to interpret them in that way, or to have purposely placed them in such a way 

  • In the same way, a book only has intentionality because a) a human mind made them ‘about’ something and b) a human mind is interpreting them to be ‘about’ something

We can generalise from this and say that any arrangement of matter cannot, on its own, be about anything else. 

All it could be would be the arrangement that it is.

So any arrangement of neurons in your brain could not be about anything else. 

So intentional states such as beliefs and desires are irreducible to the physical.

P1. Intentionality cannot be a property of any physical system

P2. Brain states are part of a physical system 

C1. So brain states cannot have intentionality

P3. Some mental states have intentionality

C2. So some mental states are not identical to brain states and MBTIT fails

It's been suggested that the inner workings of the brain are able to have intentionality by somehow resembling the thing they are 'about'. 

It has - equally vaguely been suggested that the inner workings of the brain have intentionality by being caused by something (eg. thought of a dog is about a dog because it's caused by a dog).

Dualism offers a much more coherent account of intentionality - as the mind is a non-physical substance entirely distinct from the physical brain, mental states can have intentionality. 

So Ockham’s razor appears to favour dualism over MBTIT which is problematic as the strength of the latter relies on its supposed simplicity.

One difficulty for type identity theory is that it implies that it is not possible for the same type of mental state to be realised by a different type of brain state in different individuals or in the same individual at different times. 

So if you and I share the belief that it is raining, we must both have the same type of neurophysiological process going on. 

If that brain state is destroyed, the implication would be that it would be impossible for one to have that belief again. 

However, the empirical evidence suggests that this is not how the brain works. 

We are able to recover from brain damage (such as a stroke) and re-form the same types of belief, and so we must be using a different part of the brain to do so. 

The plasticity of the brain suggests that types of mental state can be realised in different types of brain state.

He argues that mental properties are not identical to physical properties because the same mental property can be related to or supervene on different physical properties. 

• For example, the brain states that relate to pain may well be different in different species, in humans and birds, say, but pain is the same mental state. 

• If this is true, there are creatures who, when they are in pain, have different physical properties from us when we are in pain. 

• SO 'being in pain' cannot be exactly the same thing as having a particular physical property.

• If there are aliens, given that they evolved completely separately from us, if they have mental states, it is extremely unlikely that they will have the same physical states as us. 

• But according to type identity theory, to have a particular mental state just is to have a particular physical state. 

• So the theory is making a very implausible prediction.

P1. It is conceivable, and therefore possible, for a being with quite a different physical constitution from us to have the same thoughts or sensations. 

P2. But it is inconceivable, and therefore impossible, for something both to have and not have a certain property. 

C1. Therefore, mental properties can't be the same as physical properties.

We should talk about 'human pain' as this is a different property from ‘fish pain'. 

We should talk of 'human thoughts' and 'alien thoughts' as they are different mental states

 But this doesn't seem plausible

• Pain is pain because of how it feels; thought is thought because of what is thought. 

• A fish and a human being in pain share something in common, which we identify as the mental property 'being in pain'. 

• If an alien believes that snow is white, and so do I, we have the same type of thought, whatever our physiology.

This is not to say that there is no relation between mental and physical properties. It is just to argue that the relation is not identity.

• We can accept that mental states are correlated with brain states in human beings, while also allowing that in different species, the same type of mental state is correlated with a different type of physical state.

It would be chauvinistic to claim that the fact that it has a different type of neurophysiology means it cannot have the same type of mental state.

If pain were identical with a brain process in humans, this would imply that other animals, because they have different types of brain, do not experience pain. 

But it is implausible to say that other animals don't feel pain. 

Therefore there must be different ways of realising pain in different types of brain and pain cannot be a particular type of neurophysiological activity.

Therefore, types of mental state cannot be identical with types of brain state.

This is not to say that mental states are not brain states, but only that they can be realised in different types of brain state.

• Ontological claims are synthetic claims about the nature of what exists (ontology)

• Ontological theories of mind are thus empirical 

  • They are based on scientific observations 

  • Whereas analytical theories are based on analysis of language (e.g. Wittgenstein's private language argument/Ryle’s category mistake)

• The ontological reduction made shows that the brain states referred to by mental states are more basic than the mental states and can explain them

• Ontological reductions always involves the reduction from more complex principles to more basic ones

• Ontological reduction is part of reductive causal explanation - the causal powers of the macrophenomenon (A) are explained as a function of the physical structure and causal powers of the microphenomenon (B) then A can be reduced to B, A = B

• Examples of ontological reductions are common in science:

  • e.g. water is identical to H2O - its ontologically reducible to H2O

  • It's not analytically true to say water = H2O  but is ontologically true

• Similarly, pain = mental state C (for example)