Archive for June, 2004

Picture: Honderich Exclusus.

Blandula There are many eye-brow raising sentences in Ted Honderich’s paper “Consciousness as Existence, Devout Physicalism, Spiritualism”, accessible on his own web-site. Not the least surprising is the confession, half-way through, that the paper was rejected by the Journal of Consciousness Studies. The lack of reserve here will be familiar to readers of Honderich’s remarkably frank autobiography “Philosopher: a kind of life”.

But what’s going on? Honderich, now retired, had a long and eminent career in philosophy. He is the former Grote Professor at University College, London; author of many magisterial works, notably on punishment, free will, and the justifications for terrorism. He has himself acted as editor for more philosophy books than you could conveniently shake a stick at. You really wouldn’t expect him to be getting many flat rejections at this stage.

Bitbucket I think I can shed some light on that. I believe the JCS must have rejected the paper because it just makes no sense. I’ve read it carefully, and it’s not that I disagree with Honderich – I just cannot make out what he is getting at. Look, he says ‘For you to be conscious of the room is, it seems, for the room somehow to exist.’ I’d like this sentence a lot better without the ‘it seems’ and the ‘somehow’, but those are minor quibbles. Can he really mean that the room’s existence is the same thing as my being conscious of it? If so, it follows that I must be conscious of everything that exists. Which is surely nonsense. Equally, if my being conscious of the room is merely a fact about the room (that it exists), the state of my brain at the time is irrelevant. So I could have exactly the same brain state while conscious of the room as I have while I’m not conscious of it. Which is also surely nonsense.

Bitbucket So what can he mean? He says that what is normally, or by some people, taken to be the contents of consciousness are in fact, more or less, consciousness itself. What could that mean? I can imagine someone declaring that the contents of a book were the book (rather than any actual physical copy of the book), but how would that apply to consciousness? It seems that if you interpret it one way it becomes vacuous (the fact that consciousness has contents is what distinguishes it from unconsciousness); if you interpret it another it becomes absurd (there is no distinction between the conscious thing and the thing it is conscious of).

Bitbucket Honderich doesn’t give us all that much help in the course of the paper. He compares his theory with hard-line materialism and with dualism (the ‘devout physicalism’ and ‘spiritualism’ of the title), and he rates it against four criteria which he seems to take as obvious, but which in fact seem rather arbitrarily chosen. None of this helps much in the basic task of grasping his meaning. At one early stage I wondered if we were heading towards some kind of idealism, but Honderich, pointing out that he is ‘not mad as a hatter’ says his views are nothing to do with Bishop Berkeley, and no kind of epiphenomenalism, either.

Blandula I think you have to remember that Honderich has been struggling with the mind-body problem since long before it became so fashionable. I think part of his reason for stressing existence is simply to short-circuit the argument from error which was still strong thirty years ago (actually it still crops up). According to that argument, the fact that we are sometimes wrong about our perceptions shows it’s really only sense-data, or images we perceive – by stressing that true consciousness involves the existence of the perceived, Honderich rules that line of thinking firmly out of court.

Blandula I don’t think the theory is quite as confusing as you maintain, but I do have a bit of difficulty deciding whether it is meant to be relativistic or absolute. Some of the things said imply that each conscious entity exists in its own perceived world, where indeed existence and consciousness coincide, but it’s also a key point for Honderich that his argument makes consciousness a straightforward physical phenomenon, amenable to physical investigation. I’m not sure how these two claims can be reconciled.

We mustn’t forget, of course, the possibility that Honderich has got it absolutely right, and cracked the ultimate mystery of consciousness – but that we’re still too stupid to understand the answer, even when it’s explained to us.

Blandula Honderich himself doesn’t seem to regard the theory as the final truth, though. He claims that it has the desirable quality of explaining its own limitations – if consciousness is like this, no wonder it seems permanently mysterious – and suggests we might see merit in several different theories – pursue several in tandem. That doesn’t seem to me an unappealing perspective.

Picture: Turing.

It’s just 50 years since Alan Turing’s tragic death. The anniversary was marked in Manchester and elsewhere, but little seems to have appeared on the Internet – perhaps surprisingly, given his importance in the development of the computer..

Turing has a number of tremendous achievements to his credit. His war-time code-breaking may be the most famous; but perhaps the most important was the idea of the Turing machine, the theoretical apparatus which defined computation and computers. It had two distinct consequences: on the one hand, it dealt with the Entscheidungsproblem, one of the key issues of 20th century mathematics; on the other, it gave rise, via Turing’s famous (1950) paper, to the period of intense optimism about artificial intelligence which I referred to earlier as the ‘Turing era’ . The curious thing is that these two consequences of the Turing machine point in opposite, almost antithetical directions.

How so? The Entscheidungsproblem, posed by Hilbert, asks whether there is any mechanical procedure for determining whether a mathematical problem is solvable. The universal Turing machine embodies and clarifies the idea of ‘mechanical’ calculation. It is a simple apparatus which prints or erases characters on a paper tape according to the rules it has been given. In spite of this extreme simplicity it can in principle carry out any mechanical computation. In theory, in fact, it can run an appropriate version of any computer program, including the ones being used to display this page. In many respects it appears to be an entirely realistic machine which could easily be put together, but it has certain other qualities which make it an impossible abstraction. For one thing, it has to have an infinite paper tape: for another, it has to be immune to malfunction, no matter how long it runs; and most fundamental of all, it has to operate with discrete states – it must switch from one physical configuration to another without any intervening half-way stages. These characteristics mean that it is actually more like a complex function than a real machine. Nevertheless, all real-world computers owe their computerhood to their resemblance to it.

The clear conception of computation which the Turing machine provided allowed Turing to show that the Entscheidungsproblem had to be answered in the negative – there is no general procedure which can deal with all mathematical problems, even in principle. In fact, Turing was slightly too late to claim full credit for this result, which had already been established by Alonzo Church using a different approach,

The thing is, this result goes naturally with Gödel’s proof of the incompleteness of arithmetic in the sense that both establish limitations of formal algorithmic calculation. Both, therefore, suggest that the kind of computation performed by machines can never fully equal the thought processes of human beings (however those may work), which do not seem to suffer the same limitations. Gödel seems to have interpreted his own work this way. In fact there is some reason to think that Turing initially took a similar view. Andrew Hodges has pointed out that after completing his work on the Entscheidungsproblem, Turing attempted to produce a formal logic based on ordinals. It seems to have been the idea that this new, ordinal-based work would provide the basis for the kind of ‘intuitive’ reasoning which Turing machines couldn’t deliver – the kind human beings used to see the truth of Gödel statements. Only when these efforts failed, it seems, did Turing look for reasons to think that machine-style computation might be good enough to deliver a real mind after all.

Looked at again in this light, the 1950 paper seems more evasive and equivocal. It is a curious paper in many ways, with its playful tone and respectful mentions of ESP and Ada, Countess of Lovelace, but it also skirts the issue. Can machines think? Well, it says, let’s consider instead whether they can pass the Turing test . If they can, well, perhaps the original question is too meaningless to worry about.

But it surely isn’t meaningless: it’s partly because we believe that people really can think that our attitude to death is so different from our attitude to switching off the computer, for example.

It seems possible, anyway, that Turing’s desire to believe that a mechanical mind was possible led him to seek ways around the negative implications of his own work. The logic of ordinals was one possibility: when that failed, the Turing Test was basically another, justifiying further work with Turing-machine style computers.

Had he lived, of course, he might eventually have changed his mind about his own Test, or found better ways of dealing with ‘intuition’. We’ll never know quite how much we lost when, punished for his homosexuality with oestrogen injections and expelled from further participation in Government work, he killed himself with a poisoned apple.

But it is a poignant thought that in the natural course of things he could still have been alive today.