Prof

by Dermot Turing

  Although it seemed to take up the full 20-foot-by-20-foot of available space, it did not have as many as 40 racks, or weigh 50 tons, and there were certainly not 13 people to operate it. The Manchester ‘baby’ computer was not going to be guilty of the American sin of much equipment prevailing over thought. But who cared that it was small and untidy and made of junkyard parts? It was the first electronic full-function computer in the United Kingdom that could actually run a program.

  Because of the improvisation, much of Newman’s Royal Society grant remained to be spent; £3,000 a year was to be used for salaries, and Alan Turing was paid out of that amount. Sir Charles Darwin might have backed Newman’s project with less warmth if he had known this was how things would turn out. Still, Newman had trumped the ACE: Newman’s computer was working and, despite its limitations, Newman and Turing could use it to work on a real problem.

  300-year-old sum

  In September 1588, as the Spanish Armada was limping home from its failed attempt to invade England, the theologian, musicologist and mathematician Marin Mersenne was born in the west of France. One of his many ideas was that numbers of the form 2n-1 are prime numbers. While it is relatively easy, if very boring, to write out numbers of the form 2n-1 in ordinary decimal notation (1, 2, 3, 7, and so forth), after a bit the rule breaks down (24-1 = 15 is not prime). Mersenne’s numbers get very big after a while, and it is very tedious indeed to test whether they can be divided by anything and so to find out whether a given Mersenne number is prime. Mersenne had made a list of numbers of the form 2n-1 up to n = 257 which he asserted were primes. But was he right?

  ‘A Marvel of Our Time’: the Manchester Electronic Brain, as shown in the Illustrated London News in 1949, was cobbled together using leftovers from Colossus.

  The first problem that we put onto – the one other thing that I was responsible for, but it’s not gone down in history I’m sure, is that the problem was to find something non-trivial to put on to our Manchester machine which had a storage of one thousand and twenty-four digits, not words, and I devised a problem, a method, of testing Mersenne primes, allowing for motor cars parking outside and a few things like that; in spite of that it did calculate. That was, I think, the first real problem that was done. It was very nice because [2n-1] in the scale of 2 is simply 1 1 1 1 1 1 … and so that’s a very nice thing for the computer.

  Newman had selected his problem with the same mental dexterity that had characterised his work at Bletchley Park. The Manchester baby flicked through the numbers, trying to divide each one by everything possible, one after another. It took about an hour to reach a verdict for the larger Mersenne numbers. And what was the answer? The Manchester computer showed that Mersenne had got some of his results wrong. 267-1 and 2257-1 aren’t prime, but 2127-1 is. The result was something to be proud of, as The Times reported:

  THE MECHANICAL BRAIN

  ANSWER FOUND TO 300 YEAR OLD SUM

  From Our Special Correspondent

  Experiments which have been in progress in this country and the United States since the end of the war to produce an efficient mechanical ‘brain’ have been successfully completed at Manchester University, where a workable ‘brain’ has been evolved. Not only is it working satisfactorily, but for the first time a machine has been brought to the point at which it can work out problems which it is practically impossible to execute on paper. The Manchester ‘mechanical mind’ was built by Professor F.C. Williams, of the Department of Electro-Technics, and is now in the hands of two university mathematicians, Professor M. H. A. Newman and Mr A. W. [sic] Turing. It has just completed, in a matter of weeks, a problem, the nature of which is not disclosed, which was started in the seventeenth century and is only just being completed by human calculation.

  Its appearance is somewhat unprepossessing. It is composed of racks of electrical apparatus consisting of a mass of untidy wires, valves, chassis, and display tubes. When in action, the cathode ray becomes a pattern of dots which shows what information is in the machine. There is a close analogy between its structure and that of the human brain. It differs from other mechanical brains in its method of storing information. The electronic method ensures that information is more readily accessible.

  CALCULUS TO SONNET

  Mr Turing said yesterday: ‘This is only a foretaste of what is to come, and only the shadow of what is going to be. We have to have some experience with the machine before we really know its capabilities. It may take years before we settle down to the new possibilities, but I do not see why it should not enter any one of the fields normally covered by the human intellect, and eventually compete on equal terms. I do not think you can even draw the line about sonnets, though the comparison is perhaps a little bit unfair because a sonnet written by a machine will be better appreciated by another machine.’

  It was pretty outrageous to extrapolate from a simple program squeezing the most out of the Manchester machine’s tiny processing capability to the composition of sonnets. But Alan had been provoked. In the way that Darwin’s evolutionary theory had caused an irruption in the establishment of the nineteenth century, the Mechanical Brain had electrified the conservatives of the twentieth.

  Game of sonnets

  Every three years an award is made to a meritorious surgeon in memory of Sir Joseph Lister, whose work in the 1880s and 1890s introduced sterility into surgery. The winner in 1948 was a Manchester neurologist, Sir Geoffrey Jefferson. Jefferson’s award was made for his ‘knowledge of the functions and structure of the nervous system, made as a philosophical biologist, practising neurosurgery’. On 9 June 1949 Sir Geoffrey presented his thank-you speech, known as the Lister Oration. His subject, under the heading ‘The Mind of Mechanical Man’, was the idiocy of the computer scientists’ notion that machines might think.

  A machine might solve problems in logic, since logic and mathematics are much the same thing. But not until a machine can write a sonnet or a concerto because of thoughts and emotions felt, and not by the chance fall of symbols, could we agree that machine equals brain. When we hear it said that wireless valves think, we may despair of language. I venture to predict that the day will never dawn when the gracious premises of the Royal Society have to be turned into garages to house the new Fellows. I end by ranging myself with the humanist Shakespeare rather than the mechanists, recalling Hamlet’s lines: ‘What a piece of work is a man! How noble in reason! how infinite in faculty; in form, in moving, how express and admirable! in action, how like an angel! in apprehension, how like a god! the beauty of the world! the paragon of animals!’

  The man behind the sonnet. Sir Geoffrey Jefferson, who debated with Alan whether machines can think.

  The reporter from The Times who was covering the speech was more intrigued by Sir Geoffrey’s mention of the Manchester computer than by his gushings about Hamlet. He had got in touch with the Computing Department and asked Alan about sonnets. Newman’s wife, Lyn, wrote about the episode in a letter to a friend:

  Did you see the extraordinary report in the Times two weeks ago on the Manchester Calculating Machine with the fantastic remarks attributed to Alan Turing? And Max’s letter the following week trying to clear things up? The Times wired Alan, who isn’t on the telephone, to ring their office, and they interviewed him on the phone. He’s wildly innocent about the ways of reporters and has a bad stammer when he’s nervous or puzzled. It was a great shock to him when he saw the Times – and to Max who had been flying back from Belfast that day. We had a wretched weekend starting at midnight on the Friday night when some subeditor of a local paper rang up to get a story. By Sunday Max was getting a bit gruff, and when he said, ‘What do you want?’ to one newspaper, the reporter replied, ‘Only to photograph your brain.’

  Alan had just contrived to annoy his new boss and there was now a danger of what might, in 1949, have become a media frenzy. M.H.A. Newman duly wrote to The Times to try to clear things up, or at any rate restore things to a state of ordinary dullness:

&nbs
p; Sir,— It may help to avoid any misunderstanding of the nature of the computing machine now being tried out in Manchester University if you will allow me to add something to the account of it in The Times of June 11. It is a ‘general purpose’ automatic computing machine of the same general type as others which are in various stages of development. All these machines will have the [property] of choosing which instruction to obey next, according to the result of the work so far completed. It is [this] that gives these machines their great flexibility and makes them capable of carrying out from a reasonably small set of instructions the enormous number of simple operations that make up the solution of large problems. It is this feature also which has interested physiologists on the look-out for possible schematic ‘models’ of the human brain.

  He went on to explain about Mersenne primes and make it all seem very mathematical and unpoetic. Good try, but as well as a photograph of the Manchester Mechanical Brain and all its unromantic wiry tangles, The Times of that day also carried the following:

  Sir,—Your Special Correspondent quotes Mr. A. W. Turing, of Manchester University, as saying that ‘the University was really interested in the investigation of the possibilities of machines for their own sake. Their research would be directed to finding the degree of intellectual activity of which a machine was capable, and to what extent it could think for itself.’ If one may judge from Professor Jefferson’s Lister oration, to which your Correspondent refers us, responsible scientists will be quick to dissociate themselves from this programme. But we must all take warning from it. Even our dialectical materialists would feel necessitated to guard themselves, like Butler’s Erewhonians, against the possible hostility of the machines. And those of us who not only confess with our lips but believe in our hearts that men are free persons (which is unintelligible if we have no unextended mind or soul, but only a brain) must ask ourselves how far Mr. Turing’s opinions are shared, or may come to be shared, by the rulers of our country.

  Yours &c.,

  ILLTYD TRETHOWAN

  Downside Abbey, Bath, June 11

  Game on. Downside is another public school and Sherborne’s great rugby-football rival. Shockingly and exceptionally, during Alan’s time at Sherborne, Downside had actually won by 38 points to 8, on an occasion when Sherborne was captained by Alan’s friend Pat Mermagen. Soon it would be time for a replay.

  It is hard to convey to the modern reader [wrote Maurice Wilkes in 1985] the seriousness with which this debate, which was after all no more than a debate about the use of words, was regarded by all sorts of people. Some people appeared to regard it as an impious act even to attempt to construct a computer. In order to understand the emotion that was released, it is, I think, necessary to remember two things. In the first place, computers exhibited a behavior far more complex than was exhibited by the simple automatic machines with which people were familiar up to that time. The result was that to a non-scientist a computer appeared like magic. It dazzled him, and he was all too ready to believe that it differed from other machines in more than degree. In the second place a discussion about how far a machine can go in imitating human beings can easily turn into a discussion about whether the human brain is to be regarded as nothing more than a machine; this raises religious and ethical issues about which human beings have long argued and felt emotion.

  Wilkes may have had cause to be grumpy in June 1949. He was trying to get ready for his own conference on ‘automatic calculating machines’ to be hosted by the Cambridge University Mathematical Laboratory, at which his own work on the machine called EDSAC – standing for Electronic Delay Storage Automatic Calculator – would be showcased. Various experts (including Newman, Wilkinson, Williams, Wilkes himself, and Turing) would speak. The conference was due to begin only a week after the Newman and Trethowan letters were published in The Times.

  Alan’s presentation at the Cambridge conference was on the ‘Checking Process for Large Routines’ – in other words, debugging programs, which people were beginning to realise was a non-trivial problem. His paper drew once again on the old Computable Numbers ideas: he had proved mathematically in 1936 that it is impossible to devise a computer program which will tell you for sure whether any other program will go into an endless loop, or, as we say nowadays, whether it will crash. Alas, his point may have been lost on the others, as Wilkes explained:

  At one point in his talk, Turing had occasion to write a few decimal numbers on the blackboard and add them up. At first none of us could follow what he was doing until we realized that he was writing the numbers backwards with their least significant digits on the left. There was quite a fashion for doing this in Manchester and at the NPL with binary numbers, presumably because that was the way the pulses appeared on a cathode ray tube, but to do it with decimal numbers and without comment was a typical Turing aberration. I really believe that it did not occur to him that a trivial matter like that could possibly affect anybody’s understanding one way or the other.

  Propaganda

  Paradoxically, at the same time Alan was working on a new paper, which, almost uniquely for Alan’s works, would contain not a single equation. This paper was written in an easy, accessible style, and it was not about mathematics and it was not about the programming of computers. Thwarted by the burial of his Intelligent Machinery paper by the NPL, Alan was having another go. This time his paper would be published. Rather than place it among the engineering or mathematical publications, it appeared in the philosophy journal Mind.

  The new paper would rival Computable Numbers for fame: while Computable Numbers presented the concept now known as the ‘Turing Machine’, the Mind paper presented the ‘Turing Test’.

  COMPUTING MACHINERY AND INTELLIGENCE

  By A. M. Turing

  1. The Imitation Game

  I propose to consider the question, ‘Can machines think?’ This should begin with definitions of the meaning of the terms ‘machine’ and ‘think.’ Instead of attempting such a definition I shall replace the question by another, which is closely related to it and is expressed in relatively unambiguous words. The new form of the problem can be described in terms of a game which we call the ‘imitation game’. It is played with three people, a man (A), a woman (B), and an interrogator (C) who may be of either sex. The interrogator stays in a room apart from the other two. The object of the game for the interrogator is to determine which of the other two is the man and which is the woman. We now ask the question, ‘What will happen when a machine takes the part of A in this game?’ Will the interrogator decide wrongly as often when the game is played like this as he does when the game is played between a man and a woman? These questions replace our original, ‘Can machines think?’

  It will simplify matters for the reader if I explain first my own beliefs in the matter. Consider first the more accurate form of the question. I believe that in about fifty years’ time it will be possible to programme computers, with a storage capacity of about 109, to make them play the imitation game so well that an average interrogator will not have more than 70 per cent chance of making the right identification after five minutes of questioning. The original question, ‘Can machines think?’ I believe to be too meaningless to deserve discussion. Nevertheless I believe that at the end of the century the use of words and general educated opinion will have altered so much that one will be able to speak of machines thinking without expecting to be contradicted.

  The Turing Test.

  Robin Gandy described the genesis of Computing Machinery and Intelligence.

  The 1950 paper was intended not so much as a penetrating contribution to philosophy but as propaganda. Turing thought the time had come for philosophers and mathematicians and scientists to take seriously the fact that computers were not merely calculating engines but were capable of behavior which must be accounted as intelligent; he sought to persuade people that this was so. He wrote this paper – unlike his mathematical papers – quickly and with enjoyment. I can remember his reading aloud t
o me some of the passages – always with a smile, sometimes with a giggle.

  In his paper, one after another, Alan demolished the counter-arguments. Very politely, Alan refers to the views of Sir Geoffrey Jefferson, and the business about sonnets:

  I am sure that Professor Jefferson does not wish to adopt the extreme and solipsist point of view. Probably he would be quite willing to accept the imitation game as a test. The game (with the player B omitted) is frequently used in practice under the name of viva voce to discover whether some one really understands something or has ‘learnt it parrot fashion.’ Let us listen in to a part of such a viva voce:

  Interrogator: In the first line of your sonnet which reads ‘Shall I compare thee to a summer’s day,’ would not ‘a spring day’ do as well or better?

  Witness: It wouldn’t scan.

  Interrogator: How about ‘a winter’s day.’ That would scan all right.

  Witness: Yes, but nobody wants to be compared to a winter’s day.

  Interrogator: Would you say Mr. Pickwick reminded you of Christmas?

  Witness: In a way.

  Interrogator: Yet Christmas is a winter’s day, and I do not think Mr. Pickwick would mind the comparison.