"History is affected by discoveries we will make in the future" - Popper

On the evening of Friday, 25 October 1946 the Cambridge Moral Science Club - a weekly discussion group for the university's philosophers and philosophy students - held one of its regular meetings. As usual, the members assembled in King's College at 8.30, in a set of rooms in the Gibbs Building - number 3 on staircase H.

That evening the guest speaker was Dr Karl Popper, down from London to deliver an innocuous-sounding paper, 'Are There Philosophical Problems?'. Among his audience was the chairman of the club, Professor Ludwig Wittgenstein, considered by many to be the most brilliant philosopher of his time. Also present was Bertrand Russell, who for decades had been a household name as a philosopher and radical campaigner.

Popper had recently been appointed to the position of Reader in Logic and Scientific Method at the London School of Economics. He came from an Austrian-Jewish background and was newly arrived in Britain, having spent the war years lecturing in New Zealand. 7We Open Society and Its Enemies, his remorseless demolition of totalitarianism, which he had begun on the day Nazi troops entered Austria and completed as the tide of war turned, had just been published in England. It had immediately won him a select group of admirers - among them Bertrand Russell.

This was the only time these three great philosophers - Russell, Wittgenstein and Popper - were together. Yet, to this day, no one can agree precisely what took place. What is clear is that there were vehement exchanges between Popper and Wittgenstein over the fundamental nature of philosophy - whether there were indeed philosophical problems (Popper) or merely puzzles (Wittgenstein). These exchanges instantly became the stuff of legend. An early version of events had Popper and Wittgenstein battling for supremacy with red-hot pokers. As Popper himself later recollected, 'In a surprisingly short time I received a letter from New Zealand asking if it was true that Wittgenstein and I had come to blows, both armed with pokers.'

Those ten or so minutes on 25 October 1946 still provoke bitter disagreement. Above all, one dispute remains heatedly alive: did Karl Popper later publish an untrue version of what happened? Did he lie?

If he did lie, it was no casual embellishing of the facts. If he lied, it directly concerned two ambitions central to his life: the defeat at a theoretical level of fashionable twentieth-century linguistic philosophy and triumph at a personal level over Wittgenstein, the sorcerer who had dogged his career.

Popper's account can be found in his intellectual autobiography, Unended Quest, published in 1974. According to this version of events, Popper put forward a series of what he insisted were real philosophical problems. Wittgenstein summarily dismissed them all. Popper recalled that Wittgenstein 'had been nervously playing with the poker', which he used 'like a conductor's baton to emphasize his assertions', and when a question came up about the status of ethics, Wittgenstein challenged him to give an example of a moral rule. 'I replied: "Not to threaten visiting lecturers with pokers." Whereupon Wittgenstein, in a rage, threw the poker down and stormed out of the room, banging the door behind him.'

When Popper died, in 1994, newspaper obituarists picked up his telling of the tale and repeated it word for word (including the wrong date for the meeting - the 26th, not the 25th.) Then, some three years after Popper's death, a memoir published in the proceedings of one of Britain's most learned bodies, the British Academy, recounted essentially the same sequence of events. It brought down a storm of protest on the head of the author, Popper's successor at the LSE, Professor John Watkins, and sparked off an acerbic exchange of letters in the pages of the London Times Literary Supplement. A fervent Wittgenstein supporter who had taken part in the meeting, Professor Peter Geach, denounced Popper's account of the meeting as 'false from beginning to end'. It was not the first time Professor Geach had made that allegation. A robust correspondence followed as other witnesses or later supporters of the protagonists piled into the fray.

There was a delightful irony in the conflicting testimonies. They had arisen between people all professionally concerned with theories of epistemology (the grounds of knowledge), understanding and truth. Yet they concerned a sequence of events where those who disagreed were eyewitnesses on crucial questions of fact.

This tale has also gripped the imagination of many writers: no biography, philosophical account or novel involving either man seems complete without a - frequently colourful - version. It has achieved the status, if not of an urban myth, then at least of an ivory-tower fable.

But why was there such anger over what took place more than half a century before, in a small room, at a regular meeting of an obscure university club, during an argument over an arcane topic? Memories of the evening had remained fresh through the decades, persisting not over a complex philosophical theory or a clash of ideologies, but over a quip and the waving - or otherwise - of a short metal rod.

What do the incident and its aftermath tell us about Wittgenstein and Popper, their remarkable personalities, their relationship and their beliefs? How significant was it that they both came from fin-de-siecle Vienna, both born into assimilated Jewish families, but with a great gulf of wealth and influence between them? And what about the crux of the evening's debate: the philosophical divide?

Wittgenstein and Popper had a profound influence on the way we address the fundamental issues of civilization, science and culture. Between them, they made pivotal contributions both to age-old problems such as what we can be said to know, how we can make advances in our knowledge, and how we should be governed, and to contemporary puzzles about the limits of language and sense, and what lies beyond those limits. Each man believed that he had freed philosophy from the mistakes of its past, and that he carried responsibility for its future. Popper saw Wittgenstein as philosophy's ultimate enemy. Yet the story of the poker goes beyond the characters and beliefs of the antagonists. It is inseparable from the story of their times, opening a window on the tumultuous and tragic history which shaped their lives and brought them together in Cambridge. And it is the story of the schism in twentieth century philosophy over the significance of language: a division between those who diagnosed traditional philosophical problems as purely linguistic entanglements and those who believed that these problems transcended language. In the end, of course, it is the story of a linguistic puzzle in itself: to whom did Popper utter what words in that room full of witnesses, and why?

Before we begin to delve into the personalities, the history and the philosophy of those ten minutes in H3, let us introduce what are fixed and ascertainable: the place, the witnesses and their avowed recollections.

Memories Are Made of This

Memory: 'I see us still, sitting at that table.' But have 1 really the same visual image - or one of those that I had then? Do I also certainly see the table and my friend from the same point of view as then, and not see myself? - Wittgenstein

The Gibbs Building of King's College is a massive, severely classical block, constructed of white Portland stone. It was designed in 1723 by James Gibbs, who was the college's second choice: the initial plan, by Nicholas Hawksmoor, one of the premier architects of the day, was too expensive, and the building's remarkable and much praised restraint in decoration was the result of King's being short of money.

Viewed from the street, King's Parade, H3 is on the right-hand side of the building, on the first floor. The echoing approach, up a flight of uncarpeted stone steps past bare walls, is chill and uninviting. The double front door leads directly into the sitting room. Two long windows with window seats overlook the spacious elegance of the college front court and, filling the view to the left, Henry VI's great limestone chapel, a supreme example of perpendicular architecture. In the silence of an October evening, the singing of King's celebrated choir will break in on donnish concentration.

The feature of H3 at the heart of this decades-long quarrel, the fireplace, is enclosed by a marble surround above which is a carved wooden mantelpiece. It is a small, black, iron affair - more The Road to Wigan Pier than Brideshead Revisited. To its right are the doors to two smaller rooms. With views over the big lawn sweeping down to the river Cam, at the time of the meeting they were a kitchen and bedroom, although they have since been converted into studies. In those days and for some years after, most members of Cambridge colleges - undergraduates and fellows alike - were expected to dart in their dressing gowns across the courts to a communal bathroom.

In 1946 the splendour of the Gibbs Building's exterior was not reflected in the state of its rooms. This was barely a year after the end of the Second World War. Blackout curtains were still hanging - a reminder of the Luftwaffe's recent threat. Paintwork was chipped and grimy, the walls in urgent need of a wash. Although its tenant was a don, Richard Braithwaite, H3 was just as neglected as the other rooms in the building, squalid, dusty and dirty. Heating was dependent on open fires - central heating and baths were not installed until after the ultra-severe winter of 1947, when even the water that collected in the gas pipes froze, blocking them and the inhabitants protected their clothes with their gowns when humping sacks of coal.

Normally, despite the eminence of many of the speakers, only fifteen or so people would turn up to the Moral Science Club; significantly, for Dr Popper there were perhaps double that number. The medley of undergraduates, graduates and dons squeezed into whatever space they could find. Most of those who had been at Wittgenstein's late-afternoon seminar, held in his barely furnished rooms at the top of a tower of Whewell's Court - across the street from the great gate of Trinity College, where he held a fellowship - rejoined him in King's.

Conducted twice weekly, these seminars offered students a mesmerizing experience. As Wittgenstein struggled with a thought there would be a long moment of agonized silence; then, when the thought was formed, a sudden burst of ferocious energy. Permission was granted for students to attend - but on condition that they were not there merely as 'tourists'. On the afternoon Of 25 October an Indian graduate, Kanti Shah, took notes. What did it mean, Wittgenstein wanted to know, to speak to oneself? 'Is this something fainter than speaking? Is it like comparing 2+2=4 on dirty paper with 2+2=4 on clean paper?' One student suggested a comparison with a 'bell dying away so that one doesn't know if one imagines or hears it'. Wittgenstein was unimpressed.

Meanwhile, in Trinity College itself, in a room once occupied by Sir Isaac Newton, Popper and Russell were drinking China tea with lemon and eating biscuits. On this chilly day, both would have had reason to be grateful for the draught excluders newly placed around the windows. It is not known what they talked about, though one account has them plotting against Wittgenstein.

Happily, philosophy appears good for longevity: of the thirty present that night, nine, now in their seventies or eighties, responded by letter, phone and, above all, e-mail from across the globe - from England, France, Austria, the United States and New Zealand - to appeals for memories of that evening. Their ranks include a former English High Court judge, Sir John Vinelott, famous both for the quiet voice with which he spoke in court and for the sharpness with which he responded to counsel who asked him to speak up. There are five professors. Professor Peter Munz had come to St John's from New Zealand and returned home to become a notable academic. His book Our Knowledge of the Searchfor Knowledge opened with the poker incident: it was, he wrote, a 'symbolic and in hindsight prophetic' watershed in twentieth-century philosophy.

Professor Stephen Toulmin is an eminent philosopher of widely ranging interests who spent the latter part of his academic career teaching at universities in the United States. He wrote such leading works as The Uses of Argument, and is co-author of a demanding revisionist text on Wittgenstein, placing his philosophy in the context of Viennese culture and fin de siecle intellectual ferment. As a young King's research fellow, he turned down a post as assistant to Karl Popper.

Professor Peter Geach, an authority on logic and the German logician Gottlob Frege (among many other things), lectured at the University of Birmingham, and then at Leeds. Professor Michael Wolff specialized in Victorian England, and his academic career took him to posts at Indiana University and the University of Massachusetts. Professor Georg Kreisel, a brilliant mathematician, taught at Stanford; Wittgenstein had declared him the most able philosopher he had ever met who was also a mathematician. Peter Gray-Lucas became an academic and then switched to business, first in steel, then photographic film, then papermaking. Stephen Plaister, who was married in the freezing winter Of 1947, became a prep-school master, teaching classics.

Wasfi Hijab deserves a special mention. He was the secretary of the Moral Science Club at the time of the fateful meeting. No real prestige was attached to the position, he says. He cannot even remember how he came to hold it - probably a case of Buggins's turn. His job as secretary was to fix the agenda for the term, which he would do after consulting with members of the faculty. In his period of office he succeeded in persuading not just Popper to travel to Cambridge, but also the man who brought the news of logical positivism from Vienna to England, A. J. Ayer. Ayer always found it an 'ordeal' to speak in front of Wittgenstein, but nevertheless replied to Hijab's invitation by saying that he would gladly talk to the society, even though in his opinion 'Cambridge philosophy was rich in technique but poor in substance.' 'That', says Hijab, 'shows how much he knew.'

Hijab's Cambridge experience says much about Wittgenstein. He had arrived in Cambridge in 1945 on a scholarship from Jerusalem, where he had taught mathematics in a secondary school. His goal was to switch disciplines by studying for a doctorate in philosophy. Three years later he left with his Ph.D. unfinished. He had made a mistake fatal to his ambitions: against all advice - from Richard Braithwaite among others - he had asked Wittgenstein to be . his supervisor. To general astonishment Wittgenstein had agreed.

Hijab remembers his tutorials well. They were, when weather permitted, ambulatory. Round and round the manicured Trinity fellows' garden they would walk: he, Wittgenstein and a fellow student Elizabeth Anscombe, deep in discussion of the philosophy of religion. 'If you want to know whether a man is religious, don't ask him, observe him,' said Wittgenstein. In his supervisor's presence Hijab was mostly struck dumb with sheer terror; in his absence, he says, he sometimes demonstrated he was catching a spark off the old master. Wittgenstein, Hijab now reflects, destroyed his intellectual foundations, his religious faith and his powers of abstract thought. The doctorate abandoned, for many years after leaving Cambridge he put all thought of philosophy aside and took up mathematics again. Wittgenstein, he says, was 'like an atomic bomb, a tornado - people just don't appreciate that'.

Nevertheless, Hijab retains that fierce loyalty to his teacher that Wittgenstein could inspire. 'People often say that all philosophy is just a footnote to Plato,' Hijab says, 'but they should add, "until Wittgenstein".' His devotion finally had its reward. In 1999 he caused a sensation at a Wittgenstein conference in Austria when he more or less gatecrashed the programme, but was then given two extra sessions for his discourses on the master, meriting a write-up in the ultra-serious Neue Zurcher Zeitung. From Austria, Hijab moved on to the Wittgenstein Archive in Cambridge, to hold seminars there. It took him, he said, half a century to recover from his 'over-exposure' to Wittgenstein. Now he wanted to make up for lost time.

For the full story of the confrontation between Wittgenstein and Popper we must wait until all the evidence is in. But there can be no better place to start than with our eyewitnesses.

Conventionally, we should feel a chill in the air as a glance around the room summons up the ghostly crowd waiting for Dr Popper to begin his paper and picks out our nine, now returned to youth, from among them. Inevitably the eye goes first to the crowning intellects of the evening. In front of the fireplace, placidly smoking his pipe, is the silver-haired Bertrand Russell. To Russell's left, facing the audience, is an apparently quiet and insignificant figure, Karl Popper. One or two of the undergraduates are noting his prominent ears - altogether out of proportion to his small stature - to joke about over a pint after the meeting. Popper is taking the measure of his adversary, whom he has thought about so much but until now never actually seen: Wittgenstein, the club's chairman, sitting to Russell's right. He too is small, but filled with nervous energy, passing his hand over his forehead as he waits to open the meeting and looking at Popper with those penetrating blue eyes and their 'intensely white and large surrounds that make you feel uncomfortable'.

Wittgenstein and Popper are our reason for being here. But now the eye moves on to the young Palestinian graduate, Wasfi Hijab, He is clutching the Moral Science Club minute book, in which he will later pen the understatement describing the confrontation of the evening: 'The meeting was unusually charged.'

It was Hijab who had sent the neatly hand written invitation to Popper and negotiated a change of date, from the club's habitual Thursday to Friday, to suit the guest. Like all such secretaries, he feels responsible for the guest's showing up and frets about his arrival until he actually sees him in the flesh. Popper's firm handshake is an early sign that his slight frame conceals an assertive personality.

Sitting nearby is one of Popper's closest friends in Cambridge, Peter Munz, researching for a postgraduate degree in history. Munz is one of only two to have studied under both Wittgenstein and Popper: he was taught by Popper in New Zealand during the war and, as a transparently earnest, bright student just a few weeks earlier had been welcomed by Wittgenstein into his Whewell's Court seminars. Munz recalls Popper pacing slowly across the room, throwing and catching a piece of chalk, never once breaking stride, and speaking in long and perfectly constructed sentences. Now he has encountered Wittgenstein, who wrestles visibly with his ideas, holding his head in his hands, occasionally throwing out staccato remarks, as though each word were as painful as plucking thorns, and muttering, 'God I am stupid today' or shouting, 'Damn my bloody soul!... Help me someone!'

Then, there is John Vinelott, at twenty-three his features still showing the strain of his recent naval service in the Far East. A chance happening during the war brought him to this spot. Before joining the Navy, he was a student of languages at London University. Then, browsing in a bookshop in Colombo, the capital of what he knew as Ceylon, now Sri Lanka, he picked up a copy of Wittgenstein's Tractatus Logico-Philosophicus and was immediately riveted. At the war's end he switched to Cambridge 'to sit at Wittgenstein's feet'. The sceptical eyes that will later disconcert so many litigants and barristers are now weighing up the guest speaker, Popper. That afternoon's session in Whewell's Court had been an even more vigorous intellectual workout than usual. Besides the puzzle of speaking to oneself, they had discussed the flexibility of the rules of mathematics. 'Suppose you had all done arithmetic within this room only,' Wittgenstein had hypothesized. 'And suppose you go into the next room. Mightn't this make 2+2--5 legitimate?' He had pushed this apparent absurdity further. 'If you came back from the next room with 20X20=600, and I said that was wrong, couldn't you say, "But it wasn't wrong in the other room."' Vinelott is still preoccupied with this. He has never before met a man of such intensity: 'incandescent with intellectual passion' will be his memory.

Near the front sits a Wittgenstein ultra: Peter Geach, a postgraduate, though currently without any official Cambridge raison d'etre. However, his wife, Elizabeth Anscombe, is a graduate student at the women's college, Newnham, and, like her husband, a member of the MSC. Tonight she is at home in Fitzwilliam Street, just beyond King's Parade, looking after their two young children. Both husband and wife are very close to Wittgenstein: she will become one of his heirs, translators and literary executors, and a leading philosopher in her own right. Wittgenstein refers to her fondly as 'old man'. A near-contemporary description of her is 'stocky ... wearing slacks and a man's jacket'. Together Elizabeth and Peter make a formidable academic couple, both with first-class degrees in what is said to be Oxford's toughest intellectual challenge, Literae Humaniores, the study of ancient Greek and Latin literature, Greek and Roman history, and ancient and modern philosophy. Their philosophy is informed by an unwavering commitment to Roman Catholicism. In Peter's case this may in part be a reaction to the fickleness of his father, who was in the habit of switching between religions every few months without apparent agonies of conscience; in Elizabeth's case to her being a convert.

Searching among the expectant crowd we can also locate Stephen Toulmin, Peter Gray-Lucas, Stephen Plaister and Georg Kreisel. All four have come to Cambridge after contributing to the war effort. Originally a student of mathematics and physics, Toulmin had been based in a radar research station. Now, at twenty-four, having given up science, he is a graduate student in philosophy: his doctoral thesis is considered of such a high standard that it will be taken for publication by Cambridge University Press even before being accepted by the examiners. He has rushed here from the cottage which he rents from G. E. Moore, the former Professor of Philosophy, and which is at the end of Moore's garden. Peter Gray-Lucas, a talented linguist, fluent in German, played his part in the war at the top-secret decoding centre at Bletchley Park, where so much of the Nazis' fighting strategy was undone. Georg Kreisel, Jewish and Austrian-born, was in the Admiralty; he is one of the few people not to be intimidated or overawed by Wittgenstein. Kreisel delights in the cruder of Wittgenstein's ceaseless stream of aphorisms, such as 'Don't try and shit higher than your arse', which Wittgenstein applied to philosophers like Popper who thought they could change the world. Stephen Plaister is less engaged with philosophy and has little contact with Wittgenstein. He will, however, always treasure one memory. After bumping into Wittgenstein and Kreisel in the street, Plaister was later told by Kreisel that Wittgenstein had liked his face. And there, standing out among the ex-servicemen for his youthful demeanour, is the fresh-faced Michael Wolff, straight from school at nineteen, and feeling a bit out of his depth.

They and the rest of our spectral phalanx are for the most part dressed in heavy sports jackets, grey flannels, regimental or school ties, perhaps a waistcoat or Fair Isle pullover. Remnants of service uniform can still be seen on those short of clothing coupons. One or two might have 'I was there' suede desert boots and cavalry-twill trousers. Wittgenstein's disciples stand out instantly for their aping of the master: casual, even sloppy, in open-neck shirts.

It is only to be expected that each of those present in that crowded room has a slightly different recollection of the night's events. Some had a restricted view. One thing happened on top of another, making the precise sequence uncertain. The flow of debate was so fast that it was difficult to follow. But most share one memory: the poker itself.

'Consider this poker,' Peter Geach hears Wittgenstein demand of Popper, picking up the poker and using it in a philosophical example. But as the discussion rages on between them, Wittgenstein is not reducing the guest to silence (the impact he is accustomed to), nor the guest silencing him (ditto). Finally, and only after having challenged assertion after assertion made by Popper, Wittgenstein gives up. At some stage he must have risen to his feet because Geach sees him walk back to his chair and sit down. He is still holding the poker in his hand. With a look of great exhaustion on his face, he leans back in his chair and stretches out his arm towards the fireplace. The poker drops on to the tiles of the hearth with a little rattle. At this point Geach's attention is caught by the host, Richard Braithwaite. Alarmed by Wittgenstein's gesticulating with the poker, he is making his way in a crouching position through the audience. He picks up the poker and somehow makes away with it. Shortly afterwards Wittgenstein rises to his feet and, in a huff, quietly leaves the meeting, shutting the door behind him.

Michael Wolff sees that Wittgenstein has the poker idly in his hand and, as he stares at the fire, is fidgeting with it. Someone says something that visibly annoys Wittgenstein. By this time Russell has become involved. Wittgenstein and Russell are both standing. Wittgenstein says, 'You misunderstand me, Russell. You always misunderstand me.' He emphasizes 'mis', and 'Russell' comes out as 'Hrussell'. Russell says, 'You're mixing things up, Wittgenstein. You always mix things up.' Russell's voice sounds a bit shrill, quite unlike when lecturing.

Peter Munz watches Wittgenstein suddenly take the poker - red hot - out of the fire and gesticulate with it angrily in front of Popper's face. Then Russell - who so far has not spoken a word - takes the pipe out of his mouth and says firmly, 'Wittgenstein, put down that poker at once!' His voice is high-pitched and somewhat scratchy. Wittgenstein complies, then, after a short wait, gets up and walks out, slamming the door.

From where Peter Gray-Lucas is sitting, Wittgenstein seems to be growing very excited about what he obviously believes is Popper's improper behaviour and is waving the poker about. Wittgenstein is acting in 'his usual grotesquely arrogant self-opinionated, rude and boorish manner. It made a good story afterwards to say that he had "threatened" Popper with a poker.' Stephen Plaister, too, sees the poker raised. It really seems to him the only way to deal with Popper, and he has no feeling of surprise or shock.

To Stephen Toulmin, sitting only six feet away from Wittgenstein, nothing at all out of the ordinary is occurring; nothing that in hindsight would merit the term'incident. He is focusing on Popper's attack on the idea that philosophy is meaningless and his production of various examples. A question about causality arises, and at that point Wittgenstein picks up the poker to use as a tool in order to make a point about causation. Later in the meeting - but only after Wittgenstein has left - he hears Popper state his poker principle: that one should not threaten visiting lecturers with pokers.

There is also written testimony from Hiram McLendon, an American from Harvard, who spent the academic year 19467 in Cambridge studying under Russell and was there in H3. Such an impact did the evening have on him that many years later he wrote up his memories, checking his narrative with Russell, who approved it. The florid description casts his former tutor in the role of hero - 'a towering giant, a roaring lion, a rod of reproof. Popper, he wrote, had delivered his paper almost with 'apology for its boldness'. It got a stormy reception, with those in the audience becoming increasingly agitated. Wittgenstein turned active, grabbed the iron poker, and waved it in a hostile manner, his voice rising in pitch, as he berated the visitor. Whereupon Russell, so far silent, suddenly sprang to Popper's defence, his 'bushy white hair crowning his stance' as he 'roared forth like a Sinaitic god'.

In most of these accounts the poker is imprinted on the witness's mind. But only John Vinelott sees the crucial point whether Popper makes what was probably an attempt at a joke to Wittgenstein's face - in Popper's way. Vinelott hears Popper utter his poker principle and observes that Wittgenstein is clearly annoyed at what he thinks is an unduly frivolous remark. Wittgenstein leaves the room abruptly, but there is no question of the door being slammed. Up against these versions stands Karl Popper's testimony, a detailed narrative in which he sees how Wittgenstein uses the poker for emphasis, how he demands a statement of a moral principle, and how he, Popper, responds, 'Not to threaten visiting lecturers with pokers.' He sees Wittgenstein throw down the poker and storm out, slamming the door.

How does Professor Geach deal with these divergent accounts? Manifesting the depth of passion that the incident still incites, he declares simply that Popper lied. For Geach, the crucial issue is straightforward: whether Wittgenstein left the meeting after Popper cited the poker-threat principle, as Popper claimed. Geach is certain that he saw Wittgenstein leave before that.

For his part, Professor Watkins displayed some uncertainty about his version after being challenged in the Times Literary Supplement. Following further research, he wrote to say that he was prepared to reserve judgement on exactly when Wittgenstein left the meeting - 'as a matter of detail'. It was a risky concession. After all, in Popper's autobiographical account Wittgenstein's rage had probably been caused by Popper's joking - logically impossible if Wittgenstein left before the joke. In the event as in cross-examination, to concede served only to move the advocate to still higher levels of scorn and further criticism of the witness. Disdainfully Geach rejoined, 'If somebody falsely says "John and Mary had a baby and then got married", he would not be very well defended by a friend who said his memory might have slipped as to whether the birth or the marriage came first.'

On crucial elements of the story - the sequence of events, the atmosphere, how the antagonists behaved - there are clear memories equally clearly in conflict. The poker is red-hot or it is cool. Wittgenstein gesticulates with it angrily or uses it as a baton, as an example, as a tool. He raises it, uses it for emphasis, shakes it or fidgets with it. He leaves after words with Russell or he leaves after Popper has uttered the poker principle. He leaves quietly or abruptly, slamming the door. Russell speaks in a high-pitched voice or he roars. What really happened, and why?