One-way Cartesianism

Descartes proposed a dualistic relation between the conscious, volitional soul, and the rest of the brain and body. The interface worked both ways, with (processed) sense information going in to consciousness, and volition proceeding in reverse to operate the motor system. Descartes recognised that much of what we do could be explained by more direct links between sensory stimuli and the motor system, so the soul was not essential for all actions. One-way Cartesianism is the belief in a kind of Cartesian Dualism, but where the soul is purely passive, having knowledge of what passes in the brain, but no ability to initiate actions. It has the illusion of doing so, because from its priviliged position it can see actions in preparation before they occur. The following passage from my Neurophysiology (3rd Edition, 1996; Arnolds, London) tries to explain the idea to a relatively general audience.

Roger Carpenter

'Nothing puzzles me more than time and space; and yet nothing troubles me less, as I never think about them'

Charles Lamb's reaction is not very different from that of most neurophysiologists to problems of mind, brain, and consciousness. This is of course a field that has been thoroughly dug over since the days of Descartes and Hume and indeed long before: and philosophers have every right to question whether mere empirical physiologists can add much to such a hoary debate, in which the various arguments have been rehearsed so exhaustively. But recent developments both in neurophysiology and in computer science - for £20 I can purchase an electronic device hardly bigger than a packet of cigarettes, that is the intellectual superior of half the animal kingdom - have so enlarged our notions of what classes of operation a physical system may in principle be capable of, that a great deal of earlier thought on the subject is now merely irrelevant. In a nutshell, 'brain versus mind' is no longer a matter for much argument. Functions such as speech and memory, which not so long ago were generally held to be inexplicable in physical terms, have now been irrefutably demonstrated as being carried out by particular parts of the brain, and to a large extent imitable by suitably programmed computers. So far has brain encroached on mind that it is now simply superfluous to invoke anything other than neural circuits to explain every aspect of Man's overt behaviour. Descartes' dualism proposed some non-material entity - the 'ghost in the machine' - that was provided with sense data by the sensory nerves, analysed them within itself, and then responded with appropriate actions by acting on motor nerves (the mind thus having the same relation to the body as a driver to his car: (a) below).

Clearly one must modify such a scheme to include the existence of certain automatic reflexes that clearly do not pass through the mind (b); and in fact modern neurophysiology goes further still, admitting of no other path between stimulus S and response R than unbroken chains of neural connections (c): X, the ghost in the machine, has finally been laid to rest.

Have the philosophers been wasting their time?

So is there still a problem, or have the philosophers been wasting their time? Indeed there is: that problem is consciousness. However sure I may be that (c) is a fair representation of your brain, there remains the obstinate and unshakable conviction that my brain is like (a). Though - after reading Freud - I might reluctantly agree that a great deal of what I do is not consciously willed, and that (b) is perhaps nearer the truth, nevertheless that there is no X at all is simply inconceivable. Now philosophers can have a great deal of fun with beliefs such as these, since the existence of my own consciousness is not something I can prove to other people in the way I can, for example, prove that I have hands. Clearly its outward manifestations could easily be imitated by a machine (like Hebb's example of the calculator programmed to say 'I am multiplying' every time it multiplies). But this kind of scepticism is so self-consistent as to be utterly tautological: if, like Wittgenstein, we decide that the only criterion for consciousness must be overt, public, behaviour, then of course we have nothing to say about it, because we have defined it out of existence. And for lazy neurophysiologists it provides a veneer of philosophical respectability for their unwillingness to think about the subject at all: Pavlov used to fine his students when he caught them using the words 'voluntary' or 'conscious'.

A physiological viewpoint

Yet to evade the problem by such specious materialism is perhaps no worse than to take the opposite extreme and accept consciousness as something much too mysterious and wonderful for a scientist even to be able to begin to think about. Both attitudes contribute to the evident intellectual muddle that surrounds the whole subject. So how would a brash and simple-minded physiologist proceed? Once he had accepted the reality of the phenomenon, he might go on to relate it to the fabric of the brain in much the same way as he would in the case, say, of the sense of sight. It is clear, for example, that loss of a limb does not lead to blindness, whereas loss of the eyes does; and by the use of inductive reasoning hardly more sophisticated than that, one may proceed into the brain itself and map out, almost neurone by neurone, the mechanism of the visual pathways. This kind of work has not of course been carried out systematically in the case of consciousness, if only because experiments of this sort on animals are useless to us. All the same, it is clear that we do in fact already know quite a lot about the functional anatomy of consciousness, even if we have little idea what consciousness actually is. We know, for instance, that while massive lesions of the cerebral cortex and its underlying fibres may blunt our perceptions, paralyse our limbs, impair our intelligence or even - as in the case of Phineas Gage - our morality, they have little effect on consciousness itself. Conversely, relatively slight injuries - perhaps a blow on the chin - that affect an area in the core of our brainstem (the same region of the reticular formation that is associated with arousal and sleep) can produce complete unconsciousness even though the whole of the rest of the brain is unimpaired.

At a different level of description, it is clear that we are conscious of some kinds of brain activity but not others, and that the boundaries of this zone of awareness are not fixed, but vary on occasion. By and large it is what goes on at moderately high hierarchical levels that we are conscious of, although by introspection we can often learn to increase our awareness of lower levels. Curiously enough, we also tend to be relatively unconscious of the highest levels of all, those that control our motivations; and further, even the most complex mental processes can sometimes be carried out without being conscious of the fact at all. While reading through a difficult score at the piano, I have suddenly had the realisation that for several bars I have been thinking about something entirely different, yet my brain had been getting on with the complex task of translating printed notes into finger movements perfectly well without me. Often, quite suddenly and unexpectedly when we were not thinking of it at all, we may find the solution to a problem that has baffled the most energetic conscious cerebration - perhaps, like Archimedes, in the bath; or, like Coleridge with Kubla Khan, asleep! L. S. Kubie has gone as far as to say that there is nothing we can do consciously that we cannot also do unconsciously.

A cerebral theatre

The natural conclusion must surely be that since consciousness is more associated with 'higher' functions than 'lower', yet not particularly affected by damage to precisely those regions of the brain that we know to carry out those higher functions, nor is it necessary to be conscious for those functions to be carried out perfectly adequately, that the ghost in the machine is not an executive ghost, as it is in (a) and (b), but rather a spectator, watching from its seat in the brainstem the play of activity on the cortex above it, perhaps able in some way to direct its attention from one area of interest to another, but not able to influence what is going on:

But what about free will? The ghost in such a scheme would observe the body's actions being planned, and see the commands being sent off to the muscles before the actions themselves began, and so one can well imagine how it might develop the illusion that because it knew what was going to happen, that it was itself the cause. For X, the distinction between 'I lift my arms' and 'My arms go up', in which Wittgenstein epitomised the notion of voluntary action, would amount simply to the distinction between those actions which it observed being planned, and those - such as reflex withdrawal from a hot object - which it did not. There is no implied necessity here for us to be deterministic in our actions - to an outsider we may appear to have free will - since the physical processes linking S and R can be as random and essentially unpredictable as we please. Such a scheme seems more intellectually satisfying than (a) or (b) without conflicting with our own feelings about ourselves; and unlike (c), does not merely evade the issue. The most serious objection to it is perhaps that it is difficult to see what on earth X is for, since it can't actually do anything. Perhaps it does just occasionally intervene. But in any case, what is the audience at a concert for? Or the spectators at a football match? The idea that I am being carried round by my body as a kind of perpetual tourist, a spectator of the world's stage, is not - on reflection - so very unattractive.

The moral is clear: enjoy your trip!

Do you disagree? Tell me!

Are there moral or social consequences to all this?
Some writings on this and related topics from Dr Harry West - strongly recommended.

See also:
Carpenter, R. H. S. (1999). A neural mechanism that randomises behaviour. Journal of Consciousness Studies, 6, 13-22.
Colyer, E. (1999). The race is on ... New Scientist, 163, N. 2202, 38-40.

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