Here is what looks like a persuasive explanation of the relationship between the body and consciousness.(The theory is set out by the American philosopher, John Searle.)

Take an ordinary kitchen table. It is an excellent example of what we mean by a solid object: it certainly feels solid when you touch it; it sounds solid when you tap it; and it looks as if it has a continuously solid surface. Put the smallest object you can find like a speck of dust on to it and it just lies there. If the surface were not solid, if it were porous or like a net or a grid, the speck would disappear down some gap or fissure. But not when it is solid.

But the table is only solid when seen as a whole. Look at it more closely through a microscope and then take the examination closer and closer, down to a smaller and smaller level and you find that the table is a collection of molecules and, inside them, of atoms. At this level, at the micro level, there is no solidity: a molecule of the wood of the table is not at all like the solid table we see with our eyes. The atoms are virtually empty with only a dot of a nucleus in a vast expanse of void.

So when we say of the table that it is a solid object, we are speaking of it on the big scale (at the macro level). Being solid is a feature of objects like tables when understood in terms of what we see with our eyes and feel with our hands. But at the micro level, the level of atoms and molecules, the table simply is not a solid thing.

Could this contrast between macro and micro provide a helpful way of considering the relationship of consciousness and the brain? At the micro level the brain is a collection of neurons and there is certainly no consciousness in individual neurons. Miniaturised explorers wandering through the brain are never going to come across a piece of imagination, a taste of Marmite, a phrase of music.

Maybe consciousness is like solidity, a feature that is evident only at the macro level, which, in this context, means the brain as a whole, the billions of neurons working together as one unit. Such a description of consciousness keeps it within the physical domain, as part of a universe composed of only one substance; unlike dualism, no non-physical substance needs to be invoked to explain it.

Does the macro-micro theory work as an explanation of consciousness? We could test it through a thought experiment which involves miniaturisation. Alice in Wonderland and Gulliver on two of his travels had the experience of a world of radically different dimensions. I am going to imagine taking two magical pills, one that will shrink me and one that will return me to my normal size.

Standing by the kitchen table just mentioned, I run my hand over it, rap it with my knuckles and try but fail to lift its solid bulk. It’s solid enough. I take the reduction pill whose effects are immediate. I become smaller and smaller. The grain of the wood now looks like roads and rivers; the surface is now as uneven as an Alpine landscape; there are gaps and hollows and the spaces between the strata of the wood widen and widen. Eventually, I find myself like a lonely traveller in space. The nearest objects seem an immense distance away as stars do to an astronaut. All around me is emptiness. I am now within one of the atoms that make up the table. I have travelled from macro to micro and I have confirmed that the feature of solidity so obvious at the level of the very large is not to be found at the level of the very, very small. Now I can take the other pill and return to normal size.

But what happens if I continue the experiment with the brain taking the place of the table? This time imagine that I start already at the miniaturised size. I am in a sea of neurons. I can identify their axons, their dendrites and synapses. I take the enlarging pill and very soon see the neurons as clusters; then I become aware of brain areas like the amygdala and the hippocampus. Eventually, I see the brain as a whole.

But I see nothing apart from the brain. I certainly do not observe consciousness in the way that I became aware of solidity. Remember that I could test and find the table to be solid: I could touch it, tap it and so on. The solid quality of the table at the macro level was available for me or for anyone else to confront, to find clear evidence of.

But it turns out that consciousness is not really comparable to solidity at all. It is not a public feature in the way that solidity is. It is not a feature of the macro level in the way that solidity is.

The macro-micro theory of consciousness certainly has an appeal, a physicalism-with-a-difference appeal, but the analogy with consciousness and the brain, in my opinion, does not work.

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Libet’s findings had clear implications: conscious choice occurred after the brain had set in motion the physical process that causes the action. If I choose to move my hand, before the moment at which the conscious choice is made, the brain has already initiated the action. Since effects must occur after causes, it seems that the conscious choice cannot be the cause of the hand movement.

If we generalise from Libet’s experiments, there are major implications for our view of mental causation, the notion that the mind is the cause of bodily action, and for our view of free will. But Libet himself came to the defence of the idea of conscious choice having causal power. He proposed that conscious choice comes into play in two ways: it can permit or it can veto an action already instigated by the brain. In short, the action begins in brain activity but it can be stopped or it can be allowed to continue by the power of conscious choice.

What are we to make of this description of the role of consciousness? First, Libet himself admits that there are no experimental techniques available for identifying whether the veto or permission is itself preceded by a readiness potential (like the readiness potential which is the first stage in the physical chain leading to the action). One might expect that if there is always a readiness potential immediately preceding the initial conscious choice, then there would be a readiness potential immediately preceding the veto or permission. If there is one, then the veto or permission is rendered just as incidental to the action as the initial conscious choice.

Second, it was pointed out in the commentary that accompanied Libets’s article that there would be something decidedly odd about a situation in which one type of conscious choice was always brain-related whereas another type of conscious choice was always brain-independent. Think what would be involved in practice. As I walk along the street, my brain instigates a chain of causes that will make my legs turn towards the door of a cake shop. A fraction of a second after that brain event I have the conscious experience of deciding to buy a cake. There are sufficient causes in terms of my physiology to dictate my subsequent behaviour. But then another process begins: I either veto the behaviour or I allow it to continue.

There are now two ways of interpreting the new situation. One way is to assume that there is a readiness potential, a brain event that precedes the veto or permission. But if this is the case, then that brain event sets in motion the action and the conscious experience of vetoing or permitting has no causal power.

The alternative is to posit the view that the conscious veto or permission is directly a cause of the action. But such a position must confront the strong case against the intervention of the conscious in the physical, particularly the notion of the causal closure of the physical domain and the difficulty of overdetermination. Furthermore, we have an additional difficulty for it now looks as though the brain operates on two quite different principles: in the case of conscious choosing the brain follows standard practice of physical-to-physical causation; in the case of the veto or permission a conscious event overrides that principle (surely, unprecedented in scientific enquiry) and acts as the cause.

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Does the mind affect the brain? Do conscious events like willing, being determined, having positive feelings influence the way the body works? It seems obvious that they do. Just consider the placebo effect. Patients suffering from a variety of illnesses have been given what appears to them to be a medicine but which actually contains no remedial properties at all. This is the placebo and the strange thing about it is that the patient who has received a placebo and not a medicine will later report that he feels better.

Now the recovery cannot be the result of any medicine since what the patient took ‘three times a day after meals’ consisted only of water, colouring and other ingredients which had no restorative proprieties at all. The only possible explanation, or so it seems, is that the desire to get better, their conscious belief and expectation that the prescription would work, was the cause of the improvement. It looks very much as though consciousness has a definite causal role here.

But what happens when we analyse the situation more closely? The patient is ill; the doctor examines him and writes out a prescription. ‘Take these’, he says, ‘and you will feel better’.

The first point to make is that, as in any conversation, there is a physical input and output. The doctor’s voice emits sound waves which impinge on the patient’s ear which transmits information to his brain. As a result of the receipt of this new information the brain undergoes a physical change.

The idea that words in speech or writing affect the brain is easy to show in extreme cases. Someone told tragic news may go into a state of shock, a physical state brought about as a consequence of verbal input.

In the case of the placebo what happens when the brain has received this new information? Research by scientists in the United States in 2005 showed the following. Fourteen volunteers were given saltwater injections in their jaw muscles to cause them pain while their brains were being scanned by a PET (positron emission tomography) machine. During the scan the volunteers were told that they were to receive a regular dose of a pain-relieving drug. In fact, they were to receive only a placebo.

They were then asked to assess the intensity of the pain at regular intervals. The scientists checked their responses against the data coming from the scan. The scientists concluded that when the volunteers believed they were receiving a pain-relieving drug (even though their belief was mistaken), their brains released natural pain-killing chemicals known as endorphins.

If this research is reliable, it seems then that it is possible to trace a purely physical chain of events that will explain the placebo effect:

1. The doctor speaks, i.e., emits sound waves.

2. Sound waves received by the ear of the patient and converted into electrical/chemical energy are transmitted to the brain

3. The brain processes this information (assimilating it into, for example, stored information about medical authority figures).

4. The brain releases the endorphins.

5. The endorphins influence those parts of the brain that correlate with the pain experienced

If considered in this way, there is no need to include the conscious state of willing or desiring in the causal process of the placebo effect.

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Consciousness is always changing. What is in our field of vision is different from one moment to the next. The mind is occupied now with a sound, now with a memory , now with a worry, a hope, a day-to-day thought. We seek some account of why our conscious states are in such constant flux. Why does this thought enter the mind? Why does that sound now end?

Some have suggested that God is the source of consciousness, that he sends our experiences directly to us. Maybe this is true. Or do our conscious states come from a physical world around us?

To talk of a physical world is to talk of that which is inferred from consciousness. We have no direct knowledge of a physical world. When we try to attain such knowledge, we find that we cannot penetrate beyond our own experiences. We do not prove that there is a door by touching: we simply confirm that we have the experience of touch.

The physical world is inferred from experience not the direct object of experience.

But what strangely we find is that once we make the inference, once we take for granted that there are things independent of us, we notice that our conscious experiences correlate time after time with events in that inferred domain.

We do not know the orange directly. We draw the conclusion that there is an orange from our seeing , tasting, smelling, touching experiences. Let us for the moment grant that there is an orange.

What we now notice is that when we remove the peel and place a piece of the orange in the mouth, we experience a special taste. Of course, if we keep strictly to what we know directly, then there is just the seeing and the tasting. But if we posit the separate existence of the orange, we find that our ‘orange’ experiences correlate with it.

So the changes in our conscious state in this and in countless other cases seem to correspond with, respond to changes in and movements of things around us.

If we return to the original point, we are now finding that, at least at first sight, the changes from one conscious state to another are not without any account at all (in addition to the account that they emanate from God). Once we grant a world of the physical , a domain inferred from consciousness, the physical and the conscious exist in some sort of relationship.

Conscious states are not completely free and unattached to the physical world. They are not like clouds floating loose and quite unconnected to the hills, roads and cities beneath them.

More like kites held by an invisible string to the hand of a child running across the fields.

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Thoughts land like birds on a pond,
the rare, the exotic,
but mainly the familiar;
they float and dive
while we, watching from secret hides,
take our pictures.

But where they come from
and where they go
we do not understand,
nor why they seek out now
this stretch of water.

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