Doctor Who_ The Turing Test Part 1

The Turing Test.

by Paul Leonard.

Acknowledgements

Books are possible only in a spirit of co-operation, sociability and mutual encouragement, which is why I write mine sulking in an attic. No one helped, no one could possibly help, except Justin Richards, by editing it and waiting for ages ages for me to deliver for me to deliver Jim Mortimore, by making copious imaginative suggestions, some of which are printed in full below Nick Walters, by giving unflagging friends.h.i.+p and support Chris Lake, Mark Leyland and Simon Lake of BFW, by reminding me I'm still a writer, just about My mother, by being there And Eve, by dragging me out of the attic and reminding me I'm a human being.

Book One

The Enigma

Chapter One.

The first question is: Am I speaking to anyone? Can anybody hear and understand this?

It will be difficult. Beyond the microphone into which I am speaking are one thousand and thirty-seven valves, working as a perfectly synchronised circuit. This machine samples my speech five thousand times per second, and makes the sampled intensities into encoded digits by means of a continuous key. That key will repeat after seven minutes, at which time I will change the position of the circuit by hand.

But this is not enough. It's true that no one can break this type of speech cipher today, but it's also true that all codes are decipherable in principle. In time everything can be understood: it's only a matter of having a sufficiently powerful Universal Machine.

It's possible, however, that no one will ever find the tape, or that it will be destroyed, or that it will rot, or that people will simply lose interest in what happened here, at the end of the war that we all think is so important now. If this is the case, then the next question becomes irrelevant to the problem. Nonetheless, I will ask it.

Is it safe to tell this story?

There are several definitions of 'safe' to deal with here. First, am I endangering the security of the United Kingdom?

Well, it's possible. There are so many secrets. The ENIGMA code, that's a secret, though people know what ENIGMA is, of course, and eventually the Cabinet papers, et cetera et cetera, will be released, and everyone will know the full story. How the code was broken, and what that meant for the conduct of the war. But as for the rest the events I lived through in those strange last months of the conflict n.o.body except Greene knows about them, and perhaps the American, h.e.l.ler, for some of it.

And the Doctor. Of course, the Doctor.

It is his story, more than any, that needs to be recorded. No that I need to record. I must admit that, if I am to get anywhere near to the truth: I need to record this story. For myself. And the worst thing is, I don't know the beginning of it, nor the end all I have is part of the middle. To discover the truth from small fragments like this a s.n.a.t.c.hed conversation in a public house, a tortured grimace as a city burned, a garbled explanation of noise and language and other worlds is all but impossible. It is like trying to break a code with no idea of the means of encipherment or the content of the message.

I will say now, however, that I do not think Greene was right: the Doctor is not an angel, though he may not be a man, exactly, either. I desired him as a man, loved him as one, but my love did not blind me, nor make me religious! Nor do I think that he was from outer s.p.a.ce, as h.e.l.ler seemed to believe in his droll American way. Not that I think that impossible the universe is too big for that. I just think it's unnecessary, as an explanation. Superfluous.

Though that leaves open the question of what the Doctor is, and what the strangers were, and whether the thing that we burned alive that night was a man or a machine.

Is there a difference between an intelligent machine and a man? You see, it is not a theoretical question for me any more.

But I should return to the problem of safety. I do intend to be careful. I will avoid detailed discussion of the codes, et cetera et cetera, and I have also changed some of the names, though Greene is so famous from his literary activities that I don't think it can do any harm to mention his. In this way, I don't think anything I say will compromise national security.

However, there is a second problem of safety, concerning the Doctor himself. Will I, by telling his story, however incomplete and speculative, be making his life unsafe? If this tape is heard and understood, people will know who he is. Or at least that he is not quite the same as the rest of us. Then they will go after him. They will want to find out more. They will try to use him, just as they used me.

But then it occurs to me that he can read this code, too, wherever he is. Perhaps, with his way of turning up in the right place at the right time, he will be the one to find and decode the tape. Perhaps he will even tell the government about it himself!

A thought occurs to me: could this be the purpose of my recording? Have I unconsciously decided that the Doctor himself will hear my words, naked and decoded? Is this an elaborate charade not a telling of what needs to be told, but only a message from me to the Doctor?

But what could I possibly say to him now? Goodbye?

Yes. That's the right thing to say. If it's only for him.

Goodbye, Doctor.

It's no good. It doesn't end like that. The 'goodbye' hypothesis is disproved: Alan Turing does need to do more to put his ghosts to rest.

Perhaps I should start again. It is only fair to begin the story in some sort of order.

So, I will start with that winter day in Oxford. The day I first met you, Doctor (for I'm sure you are listening, somewhere, some-when). It was December 1944, a fine day, and the rooftops and lawns of the colleges were covered in a hard white frost. I was to give a lecture on Computable Numbers at St John's. I had taken the bicycle along in the guard's van, and cycled up from the station. I took a long route, past Christ Church and the Botanical Gardens, because I knew I would need the exercise after the long and rather stuffy train journey. At first my mind was full of the subject of my lecture, but gradually a magical, freewheeling sense of excitement overcame me. You will say it was all a trick of the mind, or of memory, or of the clear winter suns.h.i.+ne and the blue sky, but even then, in those minutes before I met the Doctor, it was as if a great adventure were beginning. The white stony paths were as straight as solved equations, the sharp winter sun-shadows crossing the lawn as sharply defined as the boundaries of sets, the toothed walls of the College and its Chapel approaching me were like huge stone gear wheels, frozen in the middle of a suddenly comprehended calculation.

I was cycling through the garden at St John's, the dark quadrangle ahead, when I saw the Doctor for the first time. He was standing in a sharp polygon of sunlight, just inside the quadrangle, and he was talking to a griffin. The fanciful, anxious-looking creature was carved in relief into the stone arch above a doorway in the quad, its wings formally posed, its ears back like those of a harried cat. The Doctor had his back to me. He was wearing a green velvet jacket, and his hair was a blaze of gold. His body was perfectly poised in the sun, as if he were about to leap into flight.

But no, Mr Greene, he did not look like an angel. Nor even a fallen one.

However, he was striking enough that I felt I must dismount from my bicycle, and wheel it past him slowly, to get a better look.

'It doesn't talk back,' he said ruefully as I approached, without looking round.

I glanced up at the griffin. 'No,' I said. Then something, an impulse of gaiety perhaps, made me add, 'Perhaps you need to stroke it between the ears. Timothy likes that.' Timothy is my cat.

Although the Doctor was evidently an eccentric man who else talks to a statue? I was nonetheless taken aback when he jumped up into the air like a circus performer and, holding on to the iron standard of a lamp, swung himself on to the narrow sill above the carving. There he teetered for a moment, arms extended flat against the wall, his shoes dislodging small pieces of debris which clattered on to the yard. He somehow found a secure foothold, then reached down and petted the stone animal between the ears, or what would have been between the ears if it hadn't been a relief carving. 'h.e.l.lo, Timothy. Would you care for a stick of liquorice?'

There was a brief silence, and I was struck by the puzzled, almost grief-stricken expression that crossed the Doctor's face when the carving made no reply. It could have been drollery, but it seemed genuine.

Then he looked down at me, and grinned, as if it had had been a joke. 'He still doesn't talk! Did you say he was called Timothy?' been a joke. 'He still doesn't talk! Did you say he was called Timothy?'

I decided it was time to inject some sanity into the conversation. 'Timothy,' I said, precisely and quietly, 'is the name of my cat.'

'Oh, dear. I see.' He looked at the statue sidelong from his precarious perch, as if he thought it might after all be a cat.

'Perhaps it could only talk in the Middle Ages,' I suggested, trying to fit in with his mood. I was by now convinced that he was more than a little mad.

Again he gave me that puzzled and grief-stricken expression. 'Before that,' he said enigmatically. 'But I don't know exactly when.' He patted the griffin's head. 'Bye-bye, Timothy.' Another brilliant grin, and the Doctor jumped down, landing against my bicycle and knocking it flat, a wheel spinning. He stumbled to his knees.

'Never mind,' I said quickly, blus.h.i.+ng, as if it were my fault, which such accidents usually are.

He looked up from his kneeling position, and I was struck by the beauty and symmetry of his face, framed by that golden hair, and again by something in his expression: how can I describe it? It was luminous, and yet somehow pleading.

Was he mad? He seemed more like a child than a man and yet that face affected me deeply. He paid me a degree of attention that was (and here is why Greene might have thought him an angel) beyond the merely human. His stare was curious, powerful, like a monkey with a box of tricks. One could imagine that he saw straight through the face and its illusions, into the inner processes of the brain. Indeed, at this and other times, I swear that I could feel the individual nerve cells in my head being touched, as if he were looking for something. A solution, a line of proof, perhaps, in a book full of strange theorems. It was disturbing, yet I couldn't simply label it insane, even then. And I was still attracted to him. he mad? He seemed more like a child than a man and yet that face affected me deeply. He paid me a degree of attention that was (and here is why Greene might have thought him an angel) beyond the merely human. His stare was curious, powerful, like a monkey with a box of tricks. One could imagine that he saw straight through the face and its illusions, into the inner processes of the brain. Indeed, at this and other times, I swear that I could feel the individual nerve cells in my head being touched, as if he were looking for something. A solution, a line of proof, perhaps, in a book full of strange theorems. It was disturbing, yet I couldn't simply label it insane, even then. And I was still attracted to him.

I imagined myself as he must see me. My face was burning red from the cold and burnished with sweat, and my hair was probably sticking out at the back as usual. There were holes in my sports jacket, and my grey flannel trousers were s.h.i.+ny with age and held up by an old red tie in place of a belt. My one concession to Oxford had been a frayed brown trilby hat, but it had kept falling off my head when I was cycling, so I had tied it to the handlebars with a piece of copper wiring I had found in my pocket.

However, the Doctor seemed as unconcerned at my dishevelled appearance as he appeared unaware of his own poise and physical beauty. He picked himself up, looked over the cycle, which was undamaged. He rescued the hat, which had worked loose and landed beneath the bare pruned stalk of a rose bush.

He said, 'I am so sorry. I wasn't concentrating at all. I haven't damaged your bike, I think, but you must let me buy you a cup of tea.'

'I have to give a lecture in a few minutes,' I replied stiffly. Confused by his stare, I was now still more embarra.s.sed. I could feel my face getting even redder, and perspiration p.r.i.c.kled in my armpits. I was as usual surrendering to that fear of intimacy that always comes upon me: a fear that springs from the fact that, once intimate, I am too trusting, too easily controlled. The mesmeric effect of the Doctor's stare only increased my disturbance.

The Doctor looked disappointed at this rejection, and began to back away. I knew I must act swiftly, if I wanted to see him again.

And I wanted wanted to see him again. to see him again.

Stuttering a little, I said, 'W w we could meet afterwards.'

He agreed at once, nodding vigorously and smiling. His face was s.h.i.+ning with excitement the childlike excitement of new friends.h.i.+p as it would be felt by a man who talks to griffins. But there were shadows there too. Ill-defined, uneasy shadows, the shadows of November woods. I almost regretted my hasty acceptance. He was beautiful, he was strange, but who was he? What had he seen? Why had his look affected me so deeply? I thought about hypnosis, spies, kidnapping all the things one reads about in cheap novels. But it wasn't entirely fanciful. In this dark time at the end of the war, anything was possible. And I was the bearer of secrets.

Nonetheless I extended a hand. 'Alan Turing, pleased to meet you.'

'You're a mathematician, aren't you?'

I blinked in surprise. The question could have been a confirmation of my worst fears that he already knew too much about me but instead, after a moment's thought, I was rea.s.sured, because I imagined he knew my name from my work, or from his own academic contacts. The knowledge made him seem safer, more respectable.

'Yes, I am. And you?'

'Among other things,' he said.

Again that hint of darkness, as if the 'other things' were not all of them the subject of innocent academic study. But then, could I say with any honesty that any of my own studies were innocent of darkness?

'I have to go,' I said. 'The High Street Tea Rooms, at two?'

He tilted his face to look straight upwards. 'The High Street?'

By way of clarification I gestured towards town. 'The High Street.'

He followed my pointing finger and smiled broadly 'That will be lovely!'

As I wheeled my bicycle away, I asked his name, but he just shook his head.

'Call me the Doctor,' he said. 'If I knew more, you would be welcome to it.'

It is now apparent that the telephone call from Hugh Alexander later that day was a coincidence. There were several occasions, during the subsequent events, when I imagined that it was not, and that the Doctor had deliberately shaped his story around me. However, on reflection. I don't think this was the case. The Doctor often used the hypnotic, almost mind-reading, effect that I described above to contrive the impression that there were large forces moving within and beyond him, but most of this was a show. For all his strangeness, he was caught up in events just as much as the rest of us. He had no more control over the action than we did, and only a little more knowledge. I'm almost sure of that.

Alexander telephoned me through the Proctor's office at St John's. He was an important man now he had taken over from me at Bletchley as the de facto de facto chief cryptologist, when I left to work on the speech encipherment at Hanslope Park. He was an excellent mathematician intelligent, intuitive, consistent. He was also a good electronics engineer and an able administrator. He deserved the job, and was certainly much better at it than I had been. But today he sounded tired, and his voice had an edge of irritation which I could detect even in the compressed tones carried by the telephone line. chief cryptologist, when I left to work on the speech encipherment at Hanslope Park. He was an excellent mathematician intelligent, intuitive, consistent. He was also a good electronics engineer and an able administrator. He deserved the job, and was certainly much better at it than I had been. But today he sounded tired, and his voice had an edge of irritation which I could detect even in the compressed tones carried by the telephone line.

'I'd like to invite you to tea, Alan,' he said. 'This afternoon.'

I started to say I had a prior engagement, but Alexander cut in, 'With marzipan and cakes.'

These were key words, which let me know that my services were required. This wasn't a social invitation. I couldn't turn it down. Alexander needed me for something.

Nonetheless I contemplated making an excuse, so that I wouldn't have to miss tea with the Doctor, but I told myself this was stupid. Many lives depended on the code-breaking at Bletchley. An hour could be critical. I would have to forego the Doctor. I agreed to meet Alexander at three o'clock. On the way to the station, I stopped at the tearooms where we'd agreed to meet and left a message for the Doctor. I couldn't give an address, much less a telephone number: I had to give my mother's address.

Of course, there was no tea at Bletchley, and certainly no marzipan or cakes. A car met me at the station, and I was rushed to a hut on the perimeter of the Park. It was flattering to be given such priority, as if I were a surgeon about to perform a critical operation, but I was melancholy. My hoped-for day off had been truncated, my strange new friend lost. I was tired of the mesh of duty in which I was caught, and wondered if I would ever escape, even when the war had ended. The sense of adventure I had felt that morning had receded, giving the whole visit to St John's the air of a lost dream.

Inside the hut it was so cold that our breath made clouds in the air, and quickly fogged up the windows. Alexander looked as tired as he'd sounded shadows under his eyes, and a slow distractedness to his movements which was most uncharacteristic. A man was with him, dressed casually in a sweater and grey flannel trousers. He introduced himself as Mr White, and said he was from the Military Intelligence HQ in St Albans. Thus, straightaway, I knew that this was a very serious matter. At the time I didn't know the true ident.i.ty of 'Mr White'. But I do remember being taken aback by the direct, almost angry challenge presented by his fierce blue eyes.

'The Germans are using a new code,' said Alexander, as we sat down. 'A form of speech encipherment.'

Since this was exactly what I was working on at Hanslope Park, I could see at once why he was asking for my help.

'There isn't very much being transmitted,' Alexander went on. 'But of course it could be very important.'

I didn't agree, and said so. The Germans had telephone communications throughout the territories that they occupied: why resort to complex encipherment of speech signals and then send them by radio? It was probably just a test, similar to my own tests at Hanslope Park. The content was likely to be trivial.

'Even so...' began Alexander, but the Intelligence man interrupted him.

'It might be that the German High Command has at long last realised that the ENIGMA code is unsafe. If so, all the field operations based on our work are in danger. Hundreds of men are at risk. It's critical that we break this code quickly, Mr Turing.'

I thought it unlikely that the Germans had suddenly begun to doubt the effectiveness of their coding machines, when they had been so stupid about it for so long, but I went along with the explanation for the time being. If we could break the speech encipherment code, we would find out. And White was correct: there were lives at stake. I might be wrong about the content. My logic might be in error. It wasn't worth taking the chance.

I moved back down to Bletchley the next day, leaving the work at Hanslope Park to Don Bayley. I was optimistic about my ability to help, and I was expecting to be gone for no more than a week or two. In fact, I asked one of the army girls to take care of Timothy, and left her only five s.h.i.+llings for his keep! Fortunately, she did not let him starve...

It was good to be living at Bletchley again. The little grey mansion with all the huts in the grounds still had something of the air of a Cambridge college a college given temporary and very basic accommodation because of war, but a home of reason and learning nonetheless. You could discuss the theory of sets with a chap you happened to meet in a corridor, and (as long as he wasn't in uniform!) you would have some hope of being understood.

However, I quickly found that the job I had come to do was going to be far more difficult than I had expected. It shouldn't have been it was the exact reverse of the work I had been engaged on at Hanslope. That is, I had to take the coded pulses of the German messages and attempt to find a pattern that, when decoded, yielded intelligible speech. But there was a difficulty.

It had already been established that the transmission was a signal of fixed length, coming from a single location near Dresden. It was even possible that it was the same message, being sent again and again, differing only in the key used to encrypt it which made it even more likely, in my view, that it was a test. But even if I accepted that a.s.sumption, which ought to have made the job comparatively easy, every method of decryption that I attempted led nowhere. I knew straightaway that a 'bombe' decoder would be no use there was far too much information. I tried using ENIGMA-like plugboards, where digits were 'switched' according to a fixed pattern. I tried varying the pattern against time, against intensity, against both, the inverse of both, the logarithm of either it made no difference. I still produced only meaningless noise, more like the twittering of birds than human speech. One tape did seem promising the output had a pattern but the frequency was far too high. I tried slowing the tape down, but the result sounded very much like a startled cow.

White heard one of these playbacks when he visited to check on my progress: his hawklike expression softened, and he muttered, 'Sounds lonely, doesn't it?'

'It's just noise,' I commented. 'I haven't made any real progress with the decoding. I wonder if it was ever speech at all.'

But White shook his head. 'It's not noise. I'm certain of that. Carry on.'

I carried on, but got no closer to an answer. Within a few days I was suffering a feeling of frustration all too familiar from the earlier years of the war: the sense of an unsolvable equation, a solution that lay somewhere just beyond numbers, maddeningly beyond my reach.