Storygram: Amanda Gefter’s “The Man Who Tried to Redeem the World with Logic”

The Storygram series, in which professional writers annotate award-winning stories to illuminate what makes a great science story great, is a joint project of The Open Notebook and the Council for the Advancement of Science Writing. It is supported by a grant from the Gordon and Betty Moore Foundation. 

Amanda Gefter is a physics writer and won a AAAS Kavli Science Journalism Award in 2015 for the following story. This annotation was done by Brendan Maher and is co-published at The Open Notebook. 

Walter Pitts was used to being bullied. He’d been born into a tough family in Prohibition-era Detroit, where his father, a boiler-maker, had no trouble raising his fists to get his way.In the space of a sentence and with spare but well-chosen details, Gefter has set a stage. This is a wonderfully cinematic intro in which we’re given just enough color to make some grand guesses as to Pitts’ early years based on flashes of information about the era and on the temperament of his father. The neighborhood boys weren’t much better. One afternoon in 1935, they chased him through the streets until he ducked into the local library to hide.And right away Gefter climbs down the ladder of abstraction from broad contextual details—the time, place, and family background—into a specific scene of Pitts running through the streets. We’re brought to ground level, following this boy and hoping to catch our breath along with him in his sanctuary. The library was familiar ground, where he had taught himself Greek, Latin, logic, and mathematics—better than home, where his father insisted he drop out of school and go to work. Outside, the world was messy. Inside, it all made sense.With sanctuary reached, Gefter pushes us one step further, into Pitts’ world, asking us to step into his very mind. We are allowed for just a moment to see the world through his eyes. It’s a tough trick reading a character’s mind—especially for a character who is dead. But the themes are so familiar and relatable that we can forgive a bit of projection. Gefter also very nicely sets up this idea of libraries and logic as a sanctuary for Pitts. It becomes a central theme, and a fulcrum for the story’s most dramatic points.

Not wanting to risk another run-in that night, Pitts stayed hidden until the library closed for the evening. Alone, he wandered through the stacks of books until he came across Principia Mathematica, a three-volume tome written by Bertrand Russell and Alfred Whitehead between 1910 and 1913, which attempted to reduce all of mathematics to pure logic. Pitts sat down and began to read. For three days he remained in the library until he had read each volume cover to cover—nearly 2,000 pages in all—and had identified several mistakes.This is the stuff of legends, of Bible stories, of superhero origins. Three days? 2,000 pages? Gefter is setting us up to start suspending—ever so slightly—our disbelief, and numbers like this, which resonate across history and literature, help by making this seem at once fantastical and familiar. Deciding that Bertrand Russell himself needed to know about these, the boy drafted a letter to Russell detailing the errors. Not only did Russell write back, he was so impressed that he invited Pitts to study with him as a graduate student at Cambridge University in England. Pitts couldn’t oblige him, though—he was only 12 years old.It is a punchline you expect. Set off, as one does, by an em dash. We know that he’s a boy. But it hits no less hard as a result. It’s a great effect. But three years later, when he heard that Russell would be visiting the University of Chicago, the 15-year-old ran away from home and headed for Illinois. He never saw his family again.On the technical side, the variation in sentence length and structure is pretty much pitch-perfect. It takes us on a rollercoaster with sentences and thoughts that move fast, then slow, then fast again. A short, final punch in the chest is generally the perfect punctuation to an intro like this, and this one delivers. On the thematic side as well, this leaves readers struggling to catch their breath. We get parallels to so many familiar narratives packed into this intro: The bookish child hiding from bullies; the three days of thought and reflection; the child prodigy besting and impressing a giant in the field; and finally, the runaway. While the details of Pitts’ early life could easily fill a book, the intro breezes through to the most exhilarating and exciting part of any journey: the first step, leaving home.

In 1923, the year that Walter Pitts was born, a 25-year-old Warren McCulloch was also digesting the Principia. But that is where the similarities ended—McCulloch could not have come from a more different world. Born into a well-to-do East Coast family of lawyers, doctors, theologians, and engineers, McCulloch attended a private boys academy in New Jersey, then studied mathematics at Haverford College in Pennsylvania, then philosophy and psychology at Yale.We often refer to paragraphs like this as “potted bios.” They’re self-contained overviews of someone’s career, with enough detail to be engaging but not so much as to be obtrusive. A successful potted bio looks effortless but rarely is. Contrasting McCulloch with Pitts helps both in the selection of pertinent and engaging details and also in moving the story forward. Gefter is foreshadowing a relationship between these two without even really having to say it. In 1923 he was at Columbia, where he was studying “experimental aesthetics” and was about to earn his medical degree in neurophysiology. But McCulloch was a philosopher at heart. He wanted to know what it means to know. Freud had just published The Ego and the Id, and psychoanalysis was all the rage.Throughout this story, Gefter also does such a nice job of placing these characters in their time contextually. Explaining a character’s thoughts about a zeitgeist is a wonderful way of not just showing what the person is like, but offering a bit of why the person is the way they are. This is also an important detail because it is ultimately the model that they are going to be challenging. McCulloch didn’t buy it—he felt certain that somehow the mysterious workings and failings of the mind were rooted in the purely mechanical firings of neurons in the brain.

Though they started at opposite ends of the socioeconomic spectrum, McCulloch and Pitts were destined to live, work, and die together.Destiny is heavy stuff. It is also possibly a little hard to swallow for a skeptically minded, scientifically astute reader. But the wonderful storytelling that Gefter has done already helped to lower my defenses. We’re in the space of myth and legend already, so why not a brush with destiny? Along the way, they would create the first mechanistic theory of the mind, the first computational approach to neuroscience, the logical design of modern computers, and the pillars of artificial intelligence. But this is more than a story about a fruitful research collaboration. It is also about the bonds of friendship, the fragility of the mind, and the limits of logic’s ability to redeem a messy and imperfect world.Nut grafs don’t often announce themselves this overtly. When I ask a writer to craft one (and I so often have to ask even the most experienced writers to do so), I tell them that this is what I want: Summarize where the action is going, and highlight the most prominent themes. I often then do work to camouflage that sort of obvious statement—“This is a story about X”—because I feel it can be jarring for the reader. But Gefter has prepared us well for such an obvious overture with storytelling that gets at the “epic-ness” of the tale you’re about to read. It comes across like a Greek chorus, which is so perfectly appropriate for a story rich in math and philosophy. Gefter talks about crafting this nut in the Q&A.

***

Standing face to face,This is an excellent way to ease the reader into a physical description of the men. They are, for a moment, posable objects for us to consider. they were an unlikely pair. McCulloch, 42 years old when he met Pitts, was a confident, gray-eyed, wild-bearded, chain-smoking philosopher-poet who lived on whiskey and ice creamThis is such an unforgettable image, with scent and flavor and sensation. Whiskey and ice cream—an unlikely pairing, like Pitts and McCulloch. One is youthful, fragile, and fleeting; the other is aged, worldly, and maybe just a little dangerous. Gefter could have easily chucked out this detail, but it is so perfectly aligned with the relationship that it would have been a sin. and never went to bed before 4 a.m. Pitts, 18, was small and shy, with a long forehead that prematurely aged him, and a squat, duck-like, bespectacled face.These are wonderful physical descriptions. Like the potted bio, the best ones seem effortless but rarely are. One of the toughest things about them, I’ve found, is that I can always imagine the subject of a story reading such a description and hating it. Perhaps they are a bit easier post-mortem? It’s a good idea to practice these things even if they won’t end up in the final cut of a story. McCulloch was a respected scientist. Pitts was a homeless runaway. He’d been hanging around the University of Chicago, working a menial job and sneaking into Russell’s lectures, where he met a young medical student named Jerome Lettvin. It was Lettvin who introduced the two men. The moment they spoke, they realized they shared a hero in common: Gottfried Leibniz.We get a lot of names here. Fortunately, to readers interested in science, many will be familiar. But the way that Gefter flicks at previous references is helpful in keeping us grounded. The 17th-century philosopher had attempted to create an alphabet of human thought, each letter of which represented a concept and could be combined and manipulated according to a set of logical rules to compute all knowledge—a vision that promised to transform the imperfect outside world into the rational sanctuary of a library.The library as sanctuary theme reappears. Gefter is solidifying this connection without bashing the reader over the head with it.

McCulloch explained to Pitts that he was trying to model the brain with a Leibnizian logical calculus. He had been inspired by the Principia, in which Russell and Whitehead tried to show that all of mathematics could be built from the ground up using basic, indisputable logic. Their building block was the proposition—the simplest possible statement, either true or false. From there, they employed the fundamental operations of logic, like the conjunction (“and”), disjunction (“or”), and negation (“not”), to link propositions into increasingly complicated networks. From these simple propositions, they derived the full complexity of modern mathematics.Making this stuff seem simple while maintaining the dizzying complexity just beneath the surface is no small feat. Gefter discusses her methods in the Q&A.

Which got McCulloch thinking about neurons. He knew that each of the brain’s nerve cells only fires after a minimum threshold has been reached: Enough of its neighboring nerve cells must send signals across the neuron’s synapses before it will fire off its own electrical spike. It occurred to McCulloch that this set-up was binary—either the neuron fires or it doesn’t.This was a bit of tragic irony for me as a reader, but I’m not sure how many others would recognize that McCulloch’s concept of a binary neuron (either firing or not, as opposed to also dampening or firing at different frequencies and intensities) would doom this approach. It’s all quite understandable given the era—the pre-dawn of the computer age where binary circuitry would reign supreme. Reminding us of that with the introduction of Turing in the next graf is a nice touch. A neuron’s signal, he realized, is a proposition, and neurons seemed to work like logic gates, taking in multiple inputs and producing a single output. By varying a neuron’s firing threshold, it could be made to perform “and,” “or,” and “not” functions.

Fresh from reading a new paper by a British mathematician named Alan TuringAgain, these little signposts putting the story in its time and place are so helpful. She doesn’t have to say what year it was. We only need to know what was being talked about at the time. which proved the possibility of a machine that could compute any function (so long as it was possible to do so in a finite number of steps), McCulloch became convinced that the brain was just such a machine—one which uses logic encoded in neural networks to compute. Neurons, he thought, could be linked together by the rules of logic to build more complex chains of thought, in the same way that the Principia linked chains of propositions to build complex mathematics.

As McCulloch explained his project, Pitts understood it immediately, and knew exactly which mathematical tools could be used. McCulloch, enchanted, invited the teen to live with him and his family in Hinsdale, a rural suburb on the outskirts of Chicago. The Hinsdale household was a bustling, free-spirited bohemia. Chicago intellectuals and literary types constantly dropped by the house to discuss poetry, psychology, and radical politics while Spanish Civil War and union songs blared from the phonograph. But late at night, when McCulloch’s wife Rook and the three children went to bed, McCulloch and Pitts alone would pour the whiskey, hunker down, and attempt to build a computational brain from the neuron up.What a lovely mental picture this scene paints. You can practically smell the hand-rolled cigarettes.

Before Pitts’ arrival, McCulloch had hit a wall: There was nothing stopping chains of neurons from twisting themselves into loops, so that the output of the last neuron in a chain became the input of the first—a neural network chasing its tail. McCulloch had no idea how to model that mathematically. From the point of view of logic, a loop smells a lot like paradox: the consequent becomes the antecedent, the effect becomes the cause. McCulloch had been labeling each link in the chain with a time stamp, so that if the first neuron fired at time t, the next one fired at t+1, and so on. But when the chains circled back, t+1 suddenly came before t.Mathematical explanations are often difficult for me to follow, but there is some nice simple logic in how Gefter lays this all out. She spares us a lot of gory details, but provides a nice thumbnail sketch of the problems they are dealing with. It moves the action of the story along well. I suspect it would be easy to get drawn into the weeds here.

Pitts knew how to tackle the problem. He used modulo mathematics, which deals with numbers that circle back around on themselves like the hours of a clock. He showed McCulloch that the paradox of time t+1 coming before time t wasn’t a paradox at all, because in his calculations “before” and “after” lost their meaning. Time was removed from the equation altogether. If one were to see a lightning bolt flash on the sky, the eyes would send a signal to the brain, shuffling it through a chain of neurons. Starting with any given neuron in the chain, you could retrace the signal’s steps and figure out just how long ago lightning struck. Unless, that is, the chain is a loop. In that case, the information encoding the lightning bolt just spins in circles, endlessly. It bears no connection to the time at which the lightning actually occurred. It becomes, as McCulloch put it, “an idea wrenched out of time.” In other words, a memory.Giving the reader just enough to come to this conclusion as it is revealed is such a delicate dance. We know that she’s building to something with this endless loop. We’re given a visual and a mental picture simultaneously. It builds from there. The quote makes it wonderfully abstract, and then Gefter crashes it to the concrete—again with wonderful variation in sentence length. Memory! We’re talking about memories, here, folks.

By the time Pitts finished calculating, he and McCulloch had on their hands a mechanistic model of the mind, the first application of computation to the brain, and the first argument that the brain, at bottom, is an information processor. By stringing simple binary neurons into chains and loops, they had shown that the brain could implement every possible logical operation and compute anything that could be computed by one of Turing’s hypothetical machines. Thanks to those ouroboric loops, they had also found a way for the brain to abstract a piece of information, hang on to it, and abstract it yet again, creating rich, elaborate hierarchies of lingering ideas in a process we call “thinking.”

McCulloch and Pitts wrote up their findings in a now-seminal paper, “A Logical Calculus of Ideas Immanent in Nervous Activity,” published in the Bulletin of Mathematical Biophysics. Their model was vastly oversimplified for a biological brain, but it succeeded at showing a proof of principle. Thought, they said, need not be shrouded in Freudian mysticism or engaged in struggles between ego and id. “For the first time in the history of science,” McCulloch announced to a group of philosophy students, “we know how we know.”

***

Pitts had found in McCulloch everything he had needed—acceptance, friendship, his intellectual other half, the father he never had.These little breaks of pure, omniscient summary are really useful and sometimes hard to execute. We refer to them sometimes as signposts or “voice of god,” but to me, in this story, I half suspected that Gefter was providing us with her version of the Greek chorus, summarizing events and telling you a little bit about the inner thoughts of the characters. Although he had only lived in Hinsdale for a short time, the runaway would refer to McCulloch’s house as home for the rest of his life. For his part, McCulloch was just as enamored. In Pitts he had found a kindred spirit, his “bootlegged collaborator,” and a mind with the technical prowess to bring McCulloch’s half-formed notions to life. As he put it in a letter of reference about Pitts, “Would I had him with me always.”¹

Pitts was soon to make a similar impression on one of the towering intellectual figures of the 20th century, the mathematician, philosopher, and founder of cybernetics, Norbert Wiener. In 1943, Lettvin brought Pitts into Wiener’s office at the Massachusetts Institute of Technology (MIT). Wiener didn’t introduce himself or make small talk. He simply walked Pitts over to a blackboard where he was working out a mathematical proof. As Wiener worked, Pitts chimed in with questions and suggestions. According to Lettvin, by the time they reached the second blackboard, it was clear that Wiener had found his new right-hand man.This is some really nice storytelling with three people doing active things in a room. The reader is invited to be the fly on the wall. Up until this point, I found myself wondering somewhat about Gefter’s sourcing. This is one of the first places in the story where we actually get to see it. These are first-hand accounts. Wiener would later write that Pitts was “without question the strongest young scientist whom I have ever met … I should be extremely astonished if he does not prove to be one of the two or three most important scientists of his generation, not merely in America but in the world at large.”This is one of the strongest quotes in the story. While we’ve been led to believe that Pitts is smart, this is the confirmation. It makes such a good argument for reading the story that I almost would have wanted to see it earlier. I probably would have done something dumb like try to sneak it into the nut graf.

So impressed was Wiener that he promised Pitts a Ph.D. in mathematics at MIT, despite the fact that he had never graduated from high school—something that the strict rules at the University of Chicago prohibited. It was an offer Pitts couldn’t refuse. By the fall of 1943, Pitts had moved into a Cambridge apartment, was enrolled as a special student at MIT, and was studying under one of the most influential scientists in the world. It was quite a long way from blue-collar Detroit.

Wiener wanted Pitts to make his model of the brain more realistic. Despite the leaps Pitts and McCulloch had made, their work had made barely a ripple among brain scientists—in part because the symbolic logic they’d employed was hard to decipher, but also because their stark and oversimplified model didn’t capture the full messiness of the biological brain. Wiener, however, understood the implications of what they’d done, and knew that a more realistic model would be game-changing. He also realized that it ought to be possible for Pitts’ neural networks to be implemented in man-made machines, ushering in his dream of a cybernetic revolution. Wiener figured that if Pitts was going to make a realistic model of the brain’s 100 billion interconnected neurons, he was going to need statistics on his side. And statistics and probability theory were Wiener’s area of expertise. After all, it had been Wiener who discovered a precise mathematical definition of information: The higher the probability, the higher the entropy and the lower the information content.Again, complex thoughts are distilled deftly.

As Pitts began his work at MIT, he realized that although genetics must encode for gross neural features, there was no way our genes could pre-determine the trillions of synaptic connections in the brain—the amount of information it would require was untenable. It must be the case, he figured, that we all start out with essentially random neural networks—highly probable states containing negligible information (a thesis that continues to be debated to the present day).It is somewhat gratifying that the challenges these scientists faced are troubling modern-day researchers. It’s an important point to make to keep the reader interested. He suspected that by altering the thresholds of neurons over time, randomness could give way to order and information could emerge. He set out to model the process using statistical mechanics. Wiener excitedly cheered him on, because he knew if such a model were embodied in a machine, that machine could learn.

“I now understand at once some seven-eighths of what Wiener says, which I am told is something of an achievement,” Pitts wrote in a letter to McCulloch in December of 1943,Another great quote. It’s a nice way to update where we are in time as well. This section does some nice work at moving the narrative along swiftly with a combination of quotes and dates. some three months after he’d arrived. His work with Wiener was “to constitute the first adequate discussion of statistical mechanics, understood in the most general possible sense, so that it includes for example the problem of deriving the psychological, or statistical, laws of behavior from the microscopic laws of neurophysiology … Doesn’t it sound fine?”

That winter, Wiener brought Pitts to a conference he organized in Princeton with the mathematician and physicist John von Neumann, who was equally impressed with Pitts’ mind. Thus formed the beginnings of the group who would become known as the cyberneticians, with Wiener, Pitts, McCulloch, Lettvin, and von Neumann its core. And among this rarified group, the formerly homeless runaway stood out. “None of us would think of publishing a paper without his corrections and approval,” McCulloch wrote. “[Pitts] was in no uncertain terms the genius of our group,” said Lettvin. “He was absolutely incomparable in the scholarship of chemistry, physics, of everything you could talk about history, botany, etc. When you asked him a question, you would get back a whole textbook … To him, the world was connected in a very complex and wonderful fashion.”²

The following June, 1945, von Neumann penned what would become a historic document entitled “First Draft of a Report on the EDVAC,” the first published description of a stored-program binary computing machine—the modern computer. The EDVAC’s predecessor, the ENIAC, which took up 1,800 square feet of space in Philadelphia, was more like a giant electronic calculator than a computer. It was possible to reprogram the thing, but it took several operators several weeks to reroute all the wires and switches to do it. Von Neumann realized that it might not be necessary to rewire the machine every time you wanted it to perform a new function. If you could take each configuration of the switches and wires, abstract them, and encode them symbolically as pure information, you could feed them into the computer the same way you’d feed it data,It is such a joy to watch our predecessors come to conclusions that seem quaint and old-fashioned today. Of course programs can be encoded, but what a leap it must have taken to get there. only now the data would include the very programs that manipulate the data. Without having to rewire a thing, you’d have a universal Turing machine.

To accomplish this, von Neumann suggested modeling the computer after Pitts and McCulloch’s neural networks. In place of neurons, he suggested vacuum tubes, which would serve as logic gates, and by stringing them together exactly as Pitts and McCulloch had discovered, you could carry out any computation. To store the programs as data, the computer would need something new: a memory. That’s where Pitts’ loops came into play.There’s a nice hall-of-mirrors effect in this passage that is very subtle and not necessarily planned. They’ve designed a neural network on the basis of the age’s rudimentary understanding of how computers could work. That network in turn helped devise more complex computers that would eventually feed back into study of the brain. Talk about a logic loop. “An element which stimulates itself will hold a stimulus indefinitely,” von Neumann wrote in his report, echoing Pitts and employing his modulo mathematics. He detailed every aspect of this new computational architecture. In the entire report, he cited only a single paper: “A Logical Calculus” by McCulloch and Pitts.

By 1946, Pitts was living on Beacon Street in Boston with Oliver Selfridge, an MIT student who would become “the father of machine perception”; Hyman Minsky, the future economist; and Lettvin. He was teaching mathematical logic at MIT and working with Wiener on the statistical mechanics of the brain. The following year, at the Second Cybernetic Conference, Pitts announced that he was writing his doctoral dissertation on probabilistic three-dimensional neural networks. The scientists in the room were floored. “Ambitious” was hardly the word to describe the mathematical skill that it would take to pull off such a feat. And yet, everyone who knew Pitts was sure that he could do it. They would be waiting with bated breath.

In a letter to the philosopher Rudolf Carnap, McCulloch catalogued Pitts’ achievements. “He is the most omniverous of scientists and scholars. He has become an excellent dye chemist, a good mammalogist, he knows the sedges, mushrooms and the birds of New England. He knows neuroanatomy and neurophysiology from their original sources in Greek, Latin, Italian, Spanish, Portuguese, and German for he learns any language he needs as soon as he needs it.Again, legendary and just on the edge of unbelievable. Things like electrical circuit theory and the practical soldering in of power, lighting, and radio circuits he does himself. In my long life, I have never seen a man so erudite or so really practical.” Even the media took notice. In June 1954, Fortune magazine ran an article featuring the 20 most talented scientists under 40; Pitts was featured, next to Claude Shannon and James Watson. Against all odds, Walter Pitts had skyrocketed into scientific stardom.Adding to our list of myths and legends, we now have Pitts as Cinderella. But it is a foreboding graf. It is one that indirectly warns of gathering storm clouds. Its intent is to segue shortly to “the fall.” In the next section, Gefter will reveal the hero’s flaw that will unravel this amazing career.

***

Some years earlier,Gefter goes into flashback mode to bring up the signs of Pitts’ depression. It is a useful device because it allows us to climb up this rollercoaster, toward soaring possibility, just before we start to descend. I tend to push for chronology in a narrative, but we mustn’t be slavish about it. Originally, she says, she played the chronology straight. She discusses this in the Q&A. in a letter to McCulloch, Pitts wrote “About once a week now I become violently homesick to talk all evening and all night to you.” Despite his success, Pitts had become homesick—and home meant McCulloch. He was coming to believe that if he could work with McCulloch again, he would be happier, more productive, and more likely to break new ground. McCulloch, too, seemed to be floundering without his bootlegged collaborator.Taking on these wonderful affectations and using them with fluidity and familiarity helps Gefter to assure the reader that she is within the inner circle here and she’s bringing you along.

Suddenly, the clouds broke. In 1952, Jerry Wiesner, associate director of MIT’s Research Laboratory of Electronics, invited McCulloch to head a new project on brain science at MIT. McCulloch jumped at the opportunity—because it meant he would be working with Pitts again. He traded his full professorship and his large Hinsdale home for a research associate title and a crappy apartment in Cambridge, and couldn’t have been happier about it. The plan for the project was to use the full arsenal of information theory, neurophysiology, statistical mechanics, and computing machines to understand how the brain gives rise to the mind.Oh, you know, just that thing that philosophers and scientists have been grappling with for centuries. Hubris: another excellent way to signpost that a great fall is coming. Lettvin, along with the young neuroscientist Patrick Wall, joined McCulloch and Pitts at their new headquarters in Building 20 on Vassar Street. They posted a sign on the door: Experimental Epistemology.

With Pitts and McCulloch together again, and with Wiener and Lettvin in the mix, everything seemed poised for progress and revolution. Neuroscience, cybernetics, artificial intelligence, computer science—it was all on the brink of an intellectual explosion. The sky—or the mind—was the limit.

There was just one person who wasn’t happy about the reunion: Wiener’s wife. Margaret Wiener was, by all accounts, a controlling, conservative prude—and she despised McCulloch’s influence on her husband.This section stopped me. The narrative of the harpy wife hell-bent on ruining all the boys’ fun struck me as a little too familiar and lopsided. McCulloch hosted wild get-togethers at his family farm in Old Lyme, Connecticut, where ideas roamed free and everyone went skinny-dipping. It had been one thing when McCulloch was in Chicago, but now he was coming to Cambridge and Margaret wouldn’t have it. And so she invented a story. She sat Wiener down and informed him that when their daughter, Barbara, had stayed at McCulloch’s house in Chicago, several of “his boys” had seduced her.Here is where I did find myself wanting a bit more of a view of the reporting. Gefter places a lot of blame at the feet of Margaret Wiener, who has no chance to defend herself. Do we know that the story was invented? Is it so hard to believe that “his boys” had seduced (or done worse to) Wiener’s daughter? It’s just not entirely clear to me why we shouldn’t give her at least some benefit of the doubt. Apparently I wasn’t the only person to be concerned that she wasn’t being treated fairly. Gefter discusses this in the Q&A. Wiener immediately sent an angry telegram to Wiesner: “Please inform [Pitts and Lettvin] that all connection between me and your projects is permanently abolished. They are your problem. Wiener.” He never spoke to Pitts again. And he never told him why.³

For Pitts, this marked the beginning of the end. Wiener, who had taken on a fatherly role in his life, now abandoned him inexplicably. For Pitts, it wasn’t merely a loss. It was something far worse than that: It defied logic.Here we come back to the sanctuary-in-logic theme that is so nicely spun out in this story. Although it is through a different lens. With cracks forming in his sacred keep, we can expect only disaster.

And then there were the frogs.A great sentence. Completely unexpected at this moody junction, it evokes more plague than scientific setback. It’s a nice tease that will set you up for another technical explanation. In the basement of Building 20 at MIT, along with a garbage can full of crickets, Lettvin kept a group of them. At the time, biologists believed that the eye was like a photographic plate that passively recorded dots of light and sent them, dot for dot, to the brain, which did the heavy lifting of interpretation.This is another one of those explanations that seems effortless but requires deep understanding of arcane (indeed apocryphal) scientific writing. She’s boiling down a misunderstanding that was likely quite technical in nature. In fact, I wonder at the number of wrong things that Gefter probably had to learn about to write this story. Lettvin decided to put the idea to the test, opening up the frog’s skulls and attaching electrodes to single fibers in their optic nerves.

Together with Pitts, McCulloch and the Chilean biologist and philosopher Humberto Maturana, he subjected the frogs to various visual experiences—brightening and dimming the lights, showing them color photographs of their natural habitat, magnetically dangling artificial flies—and recorded what the eye measured before it sent the information off to the brain. To everyone’s surprise, it didn’t merely record what it saw, but filtered and analyzed information about visual features like contrast, curvature, and movement. “The eye speaks to the brain in a language already highly organized and interpreted,” they reported in the now-seminal paper “What the Frog’s Eye Tells the Frog’s Brain,” published in 1959.

The results shook Pitts’ worldview to its core.Now we see a second crack in Pitts’ sanctuary of logic. Instead of the brain computing information digital neuron by digital neuron using the exacting implement of mathematical logic, messy, analog processes in the eye were doing at least part of the interpretive work. “It was apparent to him after we had done the frog’s eye that even if logic played a part, it didn’t play the important or central part that one would have expected,” Lettvin said. “It disappointed him. He would never admit it, but it seemed to add to his despair at the loss of Wiener’s friendship.”

The spate of bad news aggravated a depressive streak that Pitts had been struggling with for years. “I have a kind of personal woe I should like your advice on,”What wonderfully heartfelt letters. You can feel his struggle to express himself and see exactly the same man who penned the stilted and oblique poem referenced earlier in the story. With source material like this, dead characters come to life. Pitts had written to McCulloch in one of his letters. “I have noticed in the last two or three years a growing tendency to a kind of melancholy apathy or depression. [Its] effect is to make the positive value seem to disappear from the world, so that nothing seems worth the effort of doing it, and whatever I do or what happens to me ceases to matter very greatly …”

In other words, Pitts was struggling with the very logic he had sought in life. Pitts wrote that his depression might be “common to all people with an excessively logical education who work in applied mathematics: It is a kind of pessimism resulting from an inability to believe in what people call the Principle of Induction, or the principle of the Uniformity of Nature. Since one cannot prove, or even render probable a priori, that the sun should rise tomorrow, we cannot really believe it shall.”

Now, alienated from Wiener, Pitts’ despair turned lethal. He began drinking heavily and pulled away from his friends. When he was offered his Ph.D., he refused to sign the paperwork. He set fire to his dissertation along with all of his notes and his papers. Years of work—important work that everyone in the community was eagerly awaiting—he burnt it all, priceless information reduced to [highlight]entropy and ash. Pitts’ downward spiral is rendered with merciless speed and intensity. It is efficient, knowing, and ever so carefully tied in to the themes of the story. The line “priceless information reduced to entropy and ash” is so lovingly chosen and relevant. It’s perfect. After whiskey and ice cream, this is probably the most memorable symbolic image, a physical depiction of the very abstract sense of loss. It’s David Quammen–style synecdoche at its finest and most pure, using an image, the burnt pages of his thesis, to represent a much larger loss while literally representing that loss. Information and energy winking out of existence in a minute. Wiesner offered Lettvin increased support for the lab if he could recover any bits of the dissertation. But it was all gone.

Pitts remained employed by MIT, but this was little more than a technicality; he hardly spoke to anyone and would frequently disappear. “We’d go hunting for him night after night,” Lettvin said. “Watching him destroy himself was a dreadful experience.” In a way Pitts was still 12 years old. He was still beaten, still a runaway, still hiding from the world in musty libraries.Gefter is inviting us to go back in time here, to remember the intro of the story. This is a clear signal that we’re coming to the end. Such a looping structure is a standard in feature writing, but it has extra meaning in a story that deals so much with looping neural networks and memories. She tells me this was not intentional. But beyond the simple mechanics of the narrative feature, Gefter is taking this moment to psychoanalyze Pitts—possibly a mean trick to play on a scientist who she has said was trying to dismantle the squishy and illogical approaches of Freud. But she does it wonderfully. It works, again, because the themes are so familiar and relatable. Only now his books took the shape of a bottle.

***

With McCulloch, Pitts had laid the foundations for cybernetics and artificial intelligence.The Greek chorus returns. Gefter does a wonderful job of summarizing what Pitts and his crew had accomplished, and it ties back so well to the nods to time and place earlier. Again, she’s looping, and hopefully helping the reader to remember the salient points—that is, she’s telling us, here is what you are to take away from this story. They had steered psychiatry away from Freudian analysis and toward a mechanistic understanding of thought. They had shown that the brain computes and that mentation is the processing of information. In doing so, they had also shown how a machine could compute, providing the key inspiration for the architecture of modern computers. Thanks to their work, there was a moment in history when neuroscience, psychiatry, computer science, mathematical logic, and artificial intelligence were all one thing, following an idea first glimpsed by Leibniz—that man, machine, number, and mind all use information as a universal currency. What appeared on the surface to be very different ingredients of the world—hunks of metal, lumps of gray matter, scratches of ink on a page—were profoundly interchangeable.

There was a catch, though: This symbolic abstraction made the world transparent but the brain opaque. Once everything had been reduced to information governed by logic, the actual mechanics ceased to matter—the tradeoff for universal computation was ontology. Von Neumann was the first to see the problem. He expressed his concern to Wiener in a letter that anticipated the coming split between artificial intelligence on one side and neuroscience on the other. “After the great positive contribution of Turing-cum-Pitts-and-McCulloch is assimilated,” he wrote, “the situation is rather worse than better than before. Indeed these authors have demonstrated in absolute and hopeless generality that anything and everything … can be done by an appropriate mechanism, and specifically by a neural mechanism—and that even one, definite mechanism can be ‘universal.’A puzzling passage, one that gives a glimpse into the kinds of struggles Gefter must have had parsing the science. It is at once simple and grandiose. Are they arguing that they’ve figured out too much and further modeling is irrelevant? Remember what I said about hubris: It’s loudest before the fall. Inverting the argument: Nothing that we may know or learn about the functioning of the organism can give, without ‘microscopic,’ cytological work any clues regarding the further details of the neural mechanism.”

This universality made it impossible for Pitts to provide a model of the brain that was practical, and so his work was dismissed and more or less forgotten by the community of scientists working on the brain. What’s more, the experiment with the frogs had shown that a purely logical, purely brain-centered vision of thought had its limits. Nature had chosen the messiness of life over the austerity of logic, a choice Pitts likely could not comprehend.Gefter pushes her mind-reading game probably to about its limit here. It certainly is rational to believe that he was dismayed that his hypotheses wouldn’t pan out, but few scientists would see the reality of nature as a “choice” for us to comprehend. But I think I’m willing to grant that poetic license one last time. He had no way of knowing that while his ideas about the biological brain were not panning out, they were setting in motion the age of digital computing, the neural network approach to machine learning, and the so-called connectionist philosophy of mind. In his own mind, he had been defeated.

On Saturday, April 21, 1969, his hand shaking with an alcoholic’s delirium tremens, Pitts sent a letter from his room at Beth Israel Hospital in Boston to McCulloch’s room down the road at the Cardiac Intensive Care Ward at Peter Bent Brigham Hospital. “I understand you had a light coronary; … that you are attached to many sensors connected to panels and alarms continuously monitored by a nurse, and cannot in consequence turn over in bed. No doubt this is cybernetical. But it all makes me most abominably sad.”What a sweet but sad exchange! Even to the end he is finding safety and sanctuary in a mechanistic view of the brain. Pitts himself had been in the hospital for three weeks, having been admitted with liver problems and jaundice. On May 14, 1969 Walter Pitts died alone in a boarding house in Cambridge, of bleeding esophageal varices,I wish I didn’t know what these were. I commend Gefter for sparing the gore. a condition associated with cirrhosis of the liver. Four months later, McCulloch passed away, as if the existence of one without the other were simply illogical, a reverberating loop wrenched open.A truly heartbreaking ending, and one with a lot of technical prowess. It does all the things a great ending should do. It recaptures the story’s main themes—logic as sanctuary, looping of memory, and of course the friendship and interconnectedness of these two individuals—and ties them together in a beautifully constructed, resonant sentence. Using looping structures in features (specifically, returning to elements of the lede in the kicker) is common, but in this story, it almost serves as a metaphor for the science. And by completing the loop in the story arc she is begging us not to let Pitts’ work be forgotten … again.

Annotator Brendan Maher is a news features editor for Nature. He lives in central New Jersey. Follow him on Twitter @bmaher.

You may view this story in its original format at Nautilus. Brendan Maher’s Q&A with writer Amanda Gefter is at The Open Notebook.