Alan Turing: The Enigma (83 page)

The war had given him a false sense of what was possible. For him, breaking the Enigma was much easier than the problem of dealing with other people, especially with those holding power. During the war his own kind of work had been amplified into something enormously real, but only because other people had done all the work of organising coordination, and because he had Churchill’s personal backing. Now there was nobody to do
this for him, the NPL administrators not really having tried. A different person could more easily have compromised, and more effectively have fought on for the success of the project. But with him, it was all or nothing. Like his father, he had resigned from the Civil Service when the system did not work for him. Unlike his father, however, he did not moan afterwards. Indeed, he very rarely referred to his time at the NPL. It became another great blank, to add to all the others.

Despite his resignation, and all the embarrassment that surrounded it, he completed a report
⁵³
for the NPL in July and August 1948. Its almost conversational style reflected the discussions he had pursued, many at Bletchley, in advancing the idea of
Intelligent Machinery
. Although nominally the work of his sabbatical year, and written for a hard-line technical establishment, it was really a description of the dream of Bletchley Park, and reviewed in an almost nostalgic way the course of his own life rather than contributing to any practical proposals that the NPL might adopt.

Expanding upon the ideas he had publicly announced in February 1947, this time he identified some of the reasons why the concept of ‘intelligent machinery’ might be perceived by such as Darwin as a contradiction in terms:

(a) An unwillingness to admit the possibility that mankind can have any rivals in intellectual power. This occurs as much amongst intellectual people as amongst others: they have more to lose. Those who admit the possibility all agree that its realisation would be very disagreeable. The same situation arises in connection with the possibility of our being superseded by some other animal species. This is almost as disagreeable and its theoretical possibility is indisputable.

(b) A religious belief that any attempt to construct such machine is a sort of Promethean irreverence.

These objections, he wrote, ‘being purely emotional, do not really need to be refuted.’ They were like Bernard Shaw’s complaint against the first Charles Darwin, that his doctrines were ‘discouraging’. The point, however, was not to find comfort, but truth.

He next moved to what he considered a less ‘emotional’, but still erroneous objection:

(c) The very limited character of the machinery which has been used until recent times (e.g. up to 1940). This encouraged the belief that machinery was necessarily limited to extremely straightforward, possibly even to repetitive, jobs. This attitude is very well expressed by Dorothy Sayers
(The Mind of the Maker
, p. 46) .. which imagines that God, having created his Universe, has now screwed the cap on His pen, put His feet on the mantelpiece and left the work to get on with itself.’

This, to Dorothy Sayers, made a
reductio ad absurdum
of determinism. How could Lord Peter Wimsey have been laid up for all time in the motions
of the particles at the Creation? To Alan all it showed was that there was no word that expressed the ‘mechanical’ operations of machines with more than trivial logical structure. Dorothy Sayers did not know in 1941 that even the little Enigma machine was sufficiently unpredictable to keep hundreds of people in employment. He was certainly fascinated by the fact that a machine like the Delilah key generator could be perfectly deterministic at one level, while producing something apparently ‘random’ at another. It gave him a model for reconciling determination and free-will. But this did not go very far. It was the capacity of machines to
learn
that he saw as the crux of the argument. A learning machine would part company altogether with the ‘mere machine’ of common parlance.

The objection from Gödel’s theorem he answered in the same way as he had in 1947, by separating ‘intelligence’ from ‘infallibility’. This time he gave an example of how the intelligent approach could be wrong, and the accurate one stupid:

It is related that the infant Gauss was asked at school to do the addition 15 + 18 + 21 + …+ 54 (or something of the kind) and that he immediately wrote down 483, presumably having calculated it as (15 + 54) (54 – 12)/2.3 …One can …imagine a situation where the children were given a number of additions to do, of which the first 5 were all arithmetic progressions, but the 6th was say 23 + 34 + 45 …+ 100 +112+ 122 …+ 199. Gauss might have given the answer to this as if it were an arithmetic progression, not having noticed that the 9th term was 112 instead of 111. This would be a definite mistake, which the less intelligent children would not have been likely to make.

More pertinent, perhaps, would have been the unmentionable fact that although careless about detail in the cryptanalytic work, he had still been regarded as the brain behind it. Implicitly, this argument appealed to the imitation principle of ‘fair play for machines’. This also lay behind his answer to a fifth objection, that

(e) In so far as a machine can show intelligence this is to be regarded as nothing but a reflection of the intelligence of its creator.

This he described as

similar to the view that the credit for the discoveries of a pupil should be given to his teacher. In such a case the teacher would be pleased with the success of his methods of education, but would not claim the results themselves unless he had actually communicated them to his pupil. He would certainly have envisaged in very broad outline the sort of thing his pupil might be expected to do, but would not expect to foresee any sort of detail. It is already possible to produce machines where this sort of situation arises in a small degree. One can produce ‘paper machines’ for playing chess. Playing against such a machine gives a definite feeling that one is pitting one’s wits against something alive.

This idea of
teaching
a machine to improve its behaviour into ‘intelligence’ was the key to most of the positive proposals of this essay. This time he would be putting the imitation principle to a constructive use. The real point of this paper was that he was beginning to think seriously about the nature of human intelligence, and how it resembled, or differed, from that of a computer. More and more clearly as time went on, the computer became the medium for his thought, not about mathematics, but about himself and other people.

He could see two possible lines of development. There was the ‘instruction note’ view, according to which better and better programs would be written, allowing the machine to take more and more over for itself. He thought this should be done. But his dominant interest now lay in the ‘states of mind’ approach to ‘building a brain’. His guiding idea was that ‘the brain must do it somehow’, and that it had not become capable of thought by virtue of some higher being writing programs for it. There must be a way in which a machine could learn for itself, according to this line of argument, just as the brain did. He explained his view that ‘intelligence’ had not been wired into the brain at birth, in a passage showing the influence of his recent research into physiology and psychology:

Many parts of a man’s brain are definite nerve circuits required for quite definite purposes. Examples of these are the ‘centres’ which control respiration, sneezing, following moving objects with the eyes, etc: all the reflexes proper (not ‘conditioned’) are due to the activities of these definite structures in the brain. Likewise the apparatus for the more elementary analysis of shapes and sounds probably comes into this category. But the more intellectual activities of the brain are too varied to be managed on this basis. The difference between the languages spoken on the two sides of the Channel is not due to differences in development of the French-speaking and English-speaking parts of the brain. It is due to the linguistic parts having been subjected to different training. We believe then that there are large parts of the brain, chiefly in the cortex, whose function is largely indeterminate. In the infant these parts do not have much effect: the effect they have is uncoordinated. In the adult they have great and purposive effect: the form of this effect depends on the training in childhood. A large remnant of the random behaviour of infancy remains in the adult.

All this suggests that the cortex of the infant is an unorganised machine, which can be organised by suitable interfering training. The organising might result in the modification of the machine into a universal machine or something like it.

Although expressed in more modern
terms, reflecting the great debate between the protagonists of nature and nurture, this was little more than could have come from
Natural Wonders
, with its little homilies on the virtues of training the brain in childhood, and how languages and other skills could be best incorporated in the ‘remembering place’ while the brain was still receptive.

According to this view, therefore, it would be possible to start with an ‘unorganised’ machine, which he thought of as made up in a rather random way from neuron-like components, and then ‘teach’ it how to behave:

…by applying appropriate interference, mimicking education, we should hope to modify the machine until it could be relied on to produce definite reactions to certain commands.

The education that he
had in mind was of the public school variety, by the carrot and stick that the Conservative party was currently accusing Attlee of taking away from the British donkey worker:

…The training of the human child depends largely on a system of rewards and punishments, and this suggests that it ought to be possible to carry through the organising with only two interfering inputs, one for ‘pleasure’ or ‘reward’ (R) and the other for ‘pain’ or ‘punishment’ (P). One can devise a large number of such ‘pleasure-pain’ systems. …Pleasure interference has a tendency to fix the character, i.e. towards preventing it changing, whereas pain stimuli tend to disrupt the character, causing features which had become fixed to change, or to become again subject to random variation. …It is intended that pain stimuli occur when the machine’s behaviour is wrong, pleasure stimuli when it is particularly right. With appropriate stimuli on these lines, judiciously operated by the ‘teacher’, one may hope that the ‘character’ will converge towards the one desired, i.e. that wrong behaviour will tend to become rare.

If the object were simply to produce a universal machine, it would be better to design and build it directly. The point, however, was that the machine thus educated would not only acquire the capacity to carry out complicated instructions, which Alan described as like a person who ‘would have no common sense, and would obey the most ridiculous orders unflinchingly’. It would not only be able to do its duty, but would have that elusive ‘initiative’ that characterised intelligence. Nowell Smith, worrying about the development of independence of character within a system of mere routine, could not better have formulated the problem:

If the untrained infant’s mind is to become an intelligent one, it must acquire both discipline and initiative. So far we have been considering only discipline. To convert a brain or machine into a universal machine is the extremest form of discipline. Without something of this kind one cannot set up proper communication. But discipline is certainly not enough in itself to produce intelligence. That which is required in addition we call initiative. This statement will have to serve as a definition. Our task is to discover the nature of this residue as it occurs in man, and to try and copy it in machines.

Alan would have liked the idea of training a boy machine to take the initiative. He did work out an example of modifying a ‘paper machine’ into a universal machine by these means, but decided it was a ‘cheat’, because his method amounted to working out the exact internal structure, the ‘character’ of the machine, and then correcting it – more like codebreaking than teaching.

It was all very laborious on paper, and he was eager to take the next step:

I feel that more should be done on these lines. I would like to investigate other types of unorganised machine, and also to try out organising methods that would be more nearly analogous to our ‘methods of education’. I made a start on the latter but found the work altogether too laborious at present. When some electronic machines are in actual operation I hope that they will make this more feasible. It should be easy to make a model of any particular machine that one wishes to work on within such a [computer]
^*
instead of having to work with a paper machine as at present. If also one decided on quite definite ‘teaching policies’ these could also be programmed into the machine. One would then allow the whole system to run for an appreciable period, and then break in as a kind of ‘inspector of schools’ and see what progress had been made.

It was a happy thought that, like a public school, the machine could grind its way along quite deterministically, but without anyone knowing what was going on inside. They would see only the end products. There was a distinctly behaviourist flavour to all this talk of pain and pleasure buttons, but his wry use of the word ‘training’, ‘discipline’, ‘character’ and ‘initiative’ showed how this was the behaviourism of Sherborne School.

More precisely, it was the
official
description of
the school process, albeit presented as rather a joke. It bore little relationship to his own mental growth. No one had pressed any pleasure buttons to reward
his
initiative; precious few pleasure buttons at all, while the pain had been dispensed freely in order to enforce patterns of behaviour that had nothing to do with intellectual advance. The only hint of contact with his own experience was the remark that discipline was necessary for the sake of
communication
, for certainly he had to be pushed into conventional communication in order to advance. Yet even there, it had not been jabs of pain and pleasure that had stimulated his willingness to communicate, but the aura – was it pain? was it pleasure? – that surrounded the figure of Christopher Morcom. As Victor Beuttell had often said to him, it was a mystery from where his ‘intelligence’ derived, for no one had been able to
teach
him mathematics.