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A Soul's Weight

by Mary Roach

What happens when a man (or a mouse, or a leech) dies on a scale.

It was a pretty place to die. The mansion on Blue Hill Avenue was the showpiece of the Dorchester, Massachusetts estate known as Grove Hall. Four stories tall, with a porticoed porch and cliques of indolent shade trees, the mansion had been home to T.K. Jones, a wealthy merchant in the China trade. In 1864, it was bought by a physician-cum-faith-healer named Charles Cullis, who turned it into the Consumptives' Home — a charitable operation for late-stage tuberculosis (a.k.a. consumption) patients. With the discovery of antibiotics 60 years off, prayer was as useful a treatment as any then on offer. TB patients were routinely packed off to sanitariums, ostensibly to partake of rest "cures," but mainly to keep them from spreading the disease.

Had you been visiting the Consumptives' Home in April 1901, you might have been witness to a curious undertaking. A plump, meek-looking man of 34, wearing wireframe glasses and not as much hair as he once did, was stooped over the platform of an ornate Fairbanks scale, customizing the device with wooden supports and what appeared to be an army-style cot. The scale was an oversized commercial model, for weighing silk — no doubt a holdover from Jones's mercantile days.

Clearly something unorthodox was afoot. Though weight loss was a universal undertaking at the Consumptives' Home, no one needed a commercial scale to track it.

The man with the hammer was Duncan Macdougall, a respected surgeon and physician who lived in a mansion of his own, in nearby Haverhill. Macdougall was acquainted with the Consumptives' Home's attending physician, but he himself was not on staff. Nor was he treating any of the patients, or even praying for them. Quite the opposite; Macdougall was literally — perhaps even a little eagerly — waiting for them to die.

For the preceding four years of his life, Duncan Macdougall had been hatching a plan to prove the existence of the human soul. If, as most religions held, people leave their bodies behind at death and persist in the form of a soul, then mustn't this soul occupy space? "It is unthinkable," wrote Macdougall, "that personality and consciousness can be attributes of that which does not occupy space," and if they occupy space, he reasoned, they must have weight. "The question arose in my mind:  Why not weigh a man at the very moment of death?" If the beam moved, and the body lost even a fraction of an ounce, he theorized, that loss might represent the soul's departure.

Macdougall enlisted the help of two fellow physicians, Drs. Sproull and Grant, who chose not — or possibly weren't invited — to put their names on the research paper. The plan was to install a cot on the scale platform and then install a dying consumptive on the cot. Death from consumption is a still, quiet affair, and so it fit Macdougall's conditions "to a nicety," as he put it. "A consumptive dying after a long illness wasting his energies, dies with scarcely a movement to disturb the beam, their bodies are also very light, and we can be forewarned for hours that a consumptive is dying." I found his enthusiasm at once endearing and a little troubling. I imagined him addressing the ward as he canvassed for volunteers. (Macdougall wrote in the Journal of the American Society for Physical Research that he secured his subjects' consent some weeks before their deaths.) You people are just perfect for this project. A, You're easy to lift, B, you're practically comatose when you go … . Who knows what the consumptives made of it, or whether they were too out of it to know what he was asking.

At 5:30 p.m. on April 10, 1901, Patient 1's death —  "my opportunity," Macdougall called it — was declared imminent. A male of ordinary build and "standard American temperament," he was wheeled from the ward and lifted onto the scale like a depleted bolt of silk. Macdougall summoned his partners. For three hours and forty minutes, the physicians watched the man fade. In place of the more usual bedside attitudes of grief and pity, the men assumed an air of breathless, intent expectancy. I imagine you see this on the faces of NASA engineers during countdown and, possibly, on vultures'.

One doctor watched the man's chest; another, the movements of his face. Macdougall himself kept his eyes on the scale's indicator. "Suddenly, coincident with death," wrote Macdougall, "the beam end dropped with an audible stroke hitting against the lower limiting bar and remaining there with no rebound. The loss was ascertained to be three-fourths of an ounce." Which is, yes, twenty-one grams. Hollywood metricized their reference to the event for the simply reason that 21 Grams sounds better. Who's going to go see a movie called Point Seven Five Ounces

Over the years, Macdougall repeated the experiment on five more patients. A paper summarizing his findings ran in the journal American Medicine in 1907. In the months that followed, dubious M.D.s launched their criticisms in lengthy letters to the editor. Macdougall countered them all. One correspondent pointed out that the sphincter and pelvic floor muscles relax at death, and that the loss was perhaps urine and/or feces. Macdougall patiently replied that if this were the case, the weight would remain upon the bed and, therefore, upon the scale. Someone else suggested that the dying patients' final exhalation might have contributed to the drop in weight. To prove that it hadn't, Macdougall gamely climbed onto the cot and exhaled "as forcibly as possible," while Sproull watched the scale. No change was observed.

The most likely culprit was something called "insensible loss":  body weight that is continually being lost through evaporating perspiration and water vapor in one's breath. Macdougall claimed to have accounted for this. His first patient, he wrote, lost water weight at the rate of an ounce per hour, far too slowly for insensible loss to explain the sudden three-quarter-ounce drop at death.


The historical authority on insensible weight loss is a Paduan physiologist named Sanctorius. Known humdrumly as the "founding father of metabolic balance studies," Sanctorius coined the term "insensible perspiration" in 1690, in a diverting volume entitled Medicina statica [i]. To aid him in his research, Sanctorius devised an experimental scale of his own. He suspended a platform on a massive steelyard scale. The platform held a bench with a hole cut out of the center of it and a bucket underneath it, and in front of the platform stood a supper table. Out box and In box. Sanctorius sat himself down on the platform, enjoyed a meal, and then sat around on the scale for eight hours, availing himself of the bucket when needed. He then weighed, to used his exuberantly capitalized phrasings, "the Excrements of the Guts" — observing on an unrelated tangent that "the thick ones are lighter and swim." Sanctorius found that a small portion of the food weight remained unaccounted for, i.e., wasn't down there in the bucket. This he ascribed to evaporated sweat and breath vapor, which he collectively dubbed insensible perspiration.

Sanctorius calculated that an eight-pound intake of meat and drink will, over one day, yield five pounds of insensible perspiration — or an average of three ounces of sweat and breath vapor lost per hour:  three times the rate Macdougall observed. At one point Sanctorius describes the digestion of "a supper of eight pounds." [ii] It soon became clear there was little overlap between the dripping trencherman of Sanctorius's day and Macdougall's dry little consumptives. I skipped ahead to Section VI, which was all about the efforts of immoderate coitus on insensible perspiration. Sanctorius effected the quaint habit of presenting his findings in the form of aphorisms. As in, "Aphorism XXXIX:  Such a Motion of a Body as resembles that of a Dog in Coition, is more hurtful than a bare Emission of Semen; for the latter wearies only the internal Parts, but the other tires both the Bowels and the Nerves." Or "Aphorism XL:  To use Coition standing, after a meal, is hurtful; because as it is upon a full Meal, it hinders the Offices of the Bowels." Sanctorius preached that by obstructing insensible perspiration, immoderate sex led to everything from "Palpitations in the Eyebrows and Joynts" to the hardening of the tunicles of the eyes — and here we have what I surmise to be the original striking of the masturbation-makes-you-go-blind myth. Sanctorius preached a carnal moderation that seemed almost killjoy — all the more so for the book's wanton promotion of oysters as sources "of the greatest possible nourishment."


So how are we to explain Macdougall's befuddling finding? I have some theories for your consideration.

Theory the First:  Duncan Macdougall was a nutter. I was an early supporter of the nutter theory, based largely on the fact that Macdougall was a member of the Massachusetts Homeopathic Medical Society. He wrote his medical school thesis on the Law of Similars, the underlying principle of homeopathy — basically Like Cures Like. I don't know what homeopathists get up to nowadays, but back in the movement's infancy it was nutter central. The homeopathists' bible, A Dictionary of Practical Materia Medica, is a three-volume compendium of plants, animals, and minerals, and the symptoms they produce if you ingest them, which homeopathists did a lot of, perhaps accounting for the nutter situation. The central tenet was that substances that cause healthy people to get certain symptoms can cure diseases with these same symptoms. The early homeopathists spent years dosing themselves and their patients and friends with every substance they could get hold of, and carefully cataloguing the reporter symptoms. I can't vouch for the movement's contributions to the healing arts — without control groups or placebos, the Materia work is meaningless by modern research standards — but I must commend their flair for language. For example, we have alumina causing "dreams of horses, of quarrels, of vexations" and a "tingling on the face, as if it were covered with a white of egg dried." Agnus castus causes "odor before the nose, like herrings or musk," as well as "feeble erections" and — it almost goes without saying — "great sadness." And then there is chamomile, said to cause the symptom "cannot be civil to the doctor."

But at the time Duncan Macdougall went to medical school, in 1893, homeopathy was not considered a fringe branch of medicine. About half the country's medical schools — including Macdougall's alma mater, Boston University — still taught the homeopathic approach to healing. (BU had dropped it by the early 1920s.) The point is, plenty of mainstream, straight-ahead physicians practiced homeopathy in Macdougall's day.

Also working against the touchy-feely flake theory are the plentiful examples of Macdougall's consistent toe-the-line geekdom. He was class president and class orator at BU. A 1907 article in the Boston Sunday Post flatly stated that Macdougall was a believer in neither spiritualism nor psychic phenomena. A Haverhill Evening Gazette piece described him as "hard-headed and practical." Greg Laing, head of the History Room at the Haverhill Public Library, recalls visiting the Macdougall household with his parents as a boy, so I asked him about the good doctor's nutter potential. (Macdougall had died by then, but his widow and son were still living.) "God, no," said Laing. "They were such grim, straitlaced people. Really and truly, they were not esoterically inclined." I phoned Olive Macdougall, the widow of Macdougall's only grandchild. Though her husband never knew his grandfather, Olive confirmed the family's decidedly non-mystical bent. Her father-in-law, Duncan's son, was a banker and lawyer.

The writer of Duncan Macdougall's Gazette obituary tried to foist a little jollity on the man, but it was a thin effort:  "He was cheerful in the sickroom and some of his sickroom phrases and words of encouragement remain on the tongues of his patients. A few of his sickroom phrases were:  'Don't you worry, my gal, everything will be all right' and 'Don't you worry and you'll get well in a bigger hurry.'"

Macdougall was neither madman nor visionary. What he was, I'm guessing, was a henpecked little man in need of attention. Greg Laing described Macdougall's wife Mary as "a battleaxe of monumental proportion." (Perhaps a chamomile tea drinker.) "I don't think she had the slightest respect or interest in her husband's project." Macdougall got his strokes from his work. As far as I can tell, he made a habit of calling up the local papers to garner laurels where he could. "Dr. Macdougall Becomes Poet," overstates the headline when some limp doggerel ran in Life. "Dr. Macdougall Wins Great Fame," blusters another, after England's navy agreed to have its Royal Marine Bands to play Macdougall's lurching composition "The British Tar's Song." (Macdougall's nephew had a contact at the Admiralty, whom he deluged with 1,800 copies of the song.)

Theory the Second:  Macdougall's experimental protocols were as lame as his poetry. Let's look a little closer at his findings.

Macdougall weighed six patients in all, but only the first, the one described earlier, stands as a strong example of the phenomenon. Macdougall threw out Patient 6's data because the man died just as they had put him on the cot and were adjusting the beam. Number 4's data he discounted because, Macdougall wrote in American Medicine, "our scales were not finely adjusted and there was a good deal of interference by people opposed to our work." The doctor makes several references to "friction on the part of officials," and states that only the first patient was run under ideal conditions, i.e., sans friction. He doesn't specify what form this friction took, but if it affected the tests to the extent that some were thrown out, it seems reasonable to assume the officials were there in the room, hectoring Macdougall or trying to bring a halt to what he was doing. Hardly ideal conditions for a test that requires concentration and enough quiet to listen for a heartbeat.

That leaves four subjects. With the exception of Number 1, the data for all were compromised in one way or another. Number 2 stopped breathing at 4:10 a.m., but the scale didn't budge for another fifteen minutes (whereupon it registered a half-ounce drop). "We had great doubt, from the ordinary evidence," writes Macdougall in his American Medicine paper, "to say just what moment he died." If you can't tell when the man died, you can't very well claim that he lost a half ounce at the moment of death.

Number 3's weight loss happened in two phases:  a half-ounce loss at the moment of death, and then an additional loss of an entire ounce a few minutes later. Macdougall explains that the second loss might have been caused by a jarring of the scale, caused when one of his colleagues listened to the subject's heart. If pressing a stethoscope to a patient's chest disturbs the balance, as of course it would, then how did Macdougall and his colleagues presume to know the precise moment of death in any of these cases?

Number 5's data were tainted by a peculiarity of the scale. Following a three-eighths-ounce loss, three-eighths ounces of weight was added to the scale to bring it back to zero; however, the beam didn't budge for fifteen minutes. Macdougall had no explanation. Was his scale dodgy? Did Fairbanks make a reliable scale? Was it really accurate to one-fifth of an ounce? Where was a Fairbanks scale historian when you needed one?


Peggy Pearl oversees the Historical Collection of the Fairbanks Museum in St. Johnsbury, Vermont, where Franklin Fairbanks began manufacturing scales in 1830. The collection includes 30 or so antique Fairbanks scales, as well as farm implements, "tools of yesteryear," 103 years of Northern New England Weather Center records, and the Carlton Felch diaries. Peggy fielded my call with a vigor that suggested things were pretty quiet around the Historical Collection office. The Fairbanks company's scales, she said, were ubiquitous from 1830 through the first half of the twentieth century. They were the Rolls-Royce of platform scales. When I told her Macdougall used a silk scale with a capacity of 300 pounds, she faxed me two pages of Fairbanks Silk Scales from a Macdougall-era catalog.

"It combines great sensitiveness with the increase in capacity and platform," said the proud Fairbanks copy. "Very handsome in appearance." Indeed, as Macdougall had said, his scale was accurate to one-fifth of an ounce. I told Peggy the story of Macdougall and the dying consumptives, hoping she might have some nugget of Fairbanks scale minutiae that would explain the good doctor's three-quarter-ounce drop. She initially wondered whether the platform might have been inlaid, in which case, you couldn't have a cot sticking out over the sides of the platform without rendering the results, as she put it, "screwy." But the scale in the drawing had a standard suspension platform.

"That's about as far as I can take you," said Peggy. You could hear the disappointment in her voice. Peggy Pearl could tell me what the weather was on April 10, 1901, and she could tell me what Carlton Felch was up to that day, but she could not tell me whether Macdougall's cot contraption had somehow compromised the Fairbanks's renowned accuracy.


Macdougall seemed aware of his study's weaknesses, and he encouraged others to try to extend and replicate his work. He wanted to do more trials himself, but was stymied by the earlier-cited frictions with officials. Overtures to "positioned and entrenched scientific authorities" at other facilities, he writes in a letter to R. Hodgson of the American Society for Psychical Research (ASPR), were met by rebuffs. His best bet would have been the ASPR itself. Indeed, the ASPR's scientific officer, Hereward Carrington, upon hearing of Macdougall's study, wrote at length and with great gusto, in an issue of the society's journal, about the possibility of outfitting a condemned prisoner in an airtight glass hood, and placing him, electric chair and all, onto a platform scale.

In the end, Macdougall resorted to weighing some dogs on a scale he set up in his barn. Owing to the difficulty of finding dogs dying from a disease that rendered them exhausted and motionless, he immobilized and then killed them via injection — fifteen dogs in all. Not one evinced a drop in weight as it died. Macdougall's spin on this rather striking batch of conflicting data was that of the churchgoing Christian:  Animals don't have souls — or anyway, sayeth the Bible, not the eternal variety — and therefore we should expect this.

Not everyone in the soul-weighing business would agree with Macdougall there. Ten years after the American Medicine paper was published, a physics teacher at Los Angeles Polytechnic High School self-published a book called The Physical Theory of the Soul, which included a chapter detailing his adventures in mouse-soul-weighing. H. LaV. Twining, as he appears on the title page, didn't seem to like animals much, as we will see, but he gave them credit for arriving in this world with the same spiritual accoutrements as humans. "It is reasonable to conclude …" he wrote, "that all forms of life have accompanying souls … and that animals would form fit subjects … since they could be killed at will and under any chosen conditions, while human beings could not."

Over the following four pages, H. LaV. offs 30 mice on his scale, using every condition the Polytechnic supply closet would support. He suffocated them in test tubes melted shut by Bunsen burners (no weight loss). He smothered them in flasks sealed with rubber stoppers and flasks sealed with parafinned corks (no loss, and no loss). He gassed them in open flasks with cyanide pellets. Here at least he witnessed a loss:  one to two milligrams "at its last kick." H. theorized that the poison had caused the mice to "perspire violent at death," and that the lost milligrams were evaporated mouse sweat. I did a little reading on the subject of cyanide poisoning, in the form of a paper by Dr. John M. Friedberg, which helped prompt the Ninth Circuit Court of Appeals to deem cyanide executions cruel and unusual. Death by cyanide does appear to be moderately aerobic — panic, retching, seizures, violent head extension, grimaces — though excessive perspiration isn't specifically mentioned as a symptom. Excessive salivation is, however. Perhaps some seizure-flung drool escaped the confines of the flask.

A colleague suggested that the lost weight might have been air expelled from the dying rodent's lungs. No slouch, H. decided to test for this, too, a process he describes, with his characteristic flair for insensitivity, like this:  "A mouse was thrown into a tank of water." A test tube was slipped over the head of the drowning mouse to catch the air it expelled as it died, and this was weighed and found to be negligible.

H. quickly moved on to more pressing matters, such as the author of a book on Rosicrucian theory who had misstated some of H.'s conclusions and misspelled his name. "This is inexcusable," he crabbed. If humans, like mice, could be killed at will, I know just who would have been found in a tank with a test tube over his head. And along with him, the animal rights advocates who chastised Twining for his cruelty. (An account of his work had run in a local newspaper.) Here is Twining in defensive overdrive:

Nearly every person who reads these lines has suffered more from the tooth ache, a thousand times more, than any of these mice did in dying … . 

Even though suffering does not take place, there is no reason why dumb animals should not have their share of suffering. Human beings during a lifetime are subjected to hours, days, and years of mental and physical anguish inflicted upon them through no fault of their own … .

The human family lives on the products of death … . We eat either animal or vegetable food and in either case life is destroyed … . [T]o kill low forms of life is just as bad, if killing be bad at all, as the killing of the higher forms of life, and there is no need of becoming hysterical over it.

The point to take away from H.'s work is that if you put a dying mouse in a sealed container — such that moisture, expelled breath, drool, et cetera, are trapped — its weight won't change. So H. LaV.'s work with mice is in line with Duncan Macdougall's dog findings, neither showing evidence of a departing soul.


In 1998, Donald Gilbert Carpenter published a whole book about soul-weighing (Physically Weighing the Soul). It's a long book but lightweight, as light as a soul, for it exists only in cyberspace, available by download at 1stBooks.com. According to Carpenter, the reason the dogs and the mice might have shown no weight loss at death is that their souls are so light they were below the scales' detection thresholds.  Macdougall said his dog-weighing scale was accurate to one-sixteenth of an ounce (1.8 grams), but a dog's soul weights less than 1.8 grams. How do we know this is the weight of a dog's soul? Because Donald Gilbert Carpenter has calculated it. (I love this guy!) Using Macdougall's findings for human beings — that the soul weighs about 20 grams — Carpenter calculated the ratio of soul-weight to body-weight-at-birth:  one to 140. Applying this to a typical puppy birth weight, he deduced that the average dog soul weighs one gram — about half the 1.8-gram sensitivity of the scale. Same problem with Twining's mouse souls — too light to register. (But not Jesus' soul. The discarnate Jesus is calculated in Chapter 17 to weigh 364 grams — close to a pound!)

Elsewhere, Carpenter calculates the volume of the human soul — of Mac, as he prefers to call it, in honor of Duncan Macdougall. Here is how he came up with his volume amount. The smallest infant to survive at birth, he says, weighed ten ounces and had a volume of three-tenths of a quart. (I do not know the formula for calculating the volume of premature baby; perhaps he hired H. LaV. Twining to throw one into a graduated cylinder and note how much water it displaced.) The volume of the baby's Mac would be identical to its birth volume because, quoting Carpenter, "if the volume of its … Mac had been bigger than that, it would have stuck out of the child's body." Once again, Jesus is the exception. His Mac had a volume of 5.25 quarts, meaning that half a quart's worth of excess soul stuck out of his body when he was born. Carpenter surmises the protruding material took the form of a glow, rather than the more pedestrian goiter or hernia that leapt into my mind.

Carpenter points out that leprechauns have a volume similar to that of the human Mac. "This makes me suspect," he writes, "that Leprechauns … are most likely discarnate humans." This makes me, in turn, suspect that Donald Gilbert Carpenter is most likely not the staid scientist that his many equations and tables suggest. (Carpenter's bio says he knows more about materialistic research on the soul than anyone else alive, but it doesn't say what kind of degree he has or what he does for a living.)

Carpenter had not, at the time his book was published, undertaken any soul-weighing experiments himself, but he had some intriguing ideas. Rather than put dying people on scales, he though it would be instructive to do the experiment with pregnant women, and look for sudden weight gain around the moment the Mac enters the fetus — which he figures happens at forty-three days, when brain waves can first be detected. Carpenter outlines a variety of unique uses for pregnant women. On page seventy-seven he tells us, "An excellent way to de-haunt a house would be to make it the residence of newly fertilized women just prior to normal entry of the Mac into the fetus."


You may be relieved to hear that my next guest does not believe in leprechauns. He has an M.D. from Stanford and an undergraduate degree from Yale in chemical engineering, with a special interest in thermodynamics and information theory. Nor does he have a friendly nickname for the soul. He has the opposite of a friendly nickname. He calls it "the (obligatory) negative entropy (i.e., energy/weight equivalent) that is necessary to allow for the nonequilibrium meta-stable physical 'quasi-steady-state' of a living/conscious biological system." And he has a plan to weigh it.

Gerry Nahum is a professor at the Duke University School of Medicine [iii] who works in an atmospheric old building called Baker House. The building holds an unlikely mix of what I'm guessing is runover from the rest of the medical center. Nahum shares the second floor with the Brain Tumor Center, Dr. C.H. Livengood, pastoral Services, and the jolly-sounding Endocrine Fellows Office. He himself teaches obstetrics and gynecology. When I first learned this, I thought that perhaps Nahum had been scheming with Donald Gilbert Carpenter and that any day now, the two of them would be ushering forty-three-days-pregnant women onto extraordinarily sensitive Duke University scales and watching the readout for the arrival of the Mac/(obligatory) negative entropy. Hardly.

Nahum is leaning back in his desk chair, fiddling with his tie, listening to me sputter about what it is I want to know. The tie is patterned with a university logo, very much in keeping with the décor:  thirty-one framed diplomas, degrees, and award certificates.

I've just described to Nahum the experiments of Duncan Macdougall, hoping to get his professional opinion regarding what might have caused the mysterious weight losses. A flicker of worry crosses Nahum's brow. Before I arrived, we exchanged a few emails, but I failed to fully prepare him for the depths of my ignorance. My ignorance is not merely deep, it is broad; it is a vast ocean that takes in chemistry, physics, information theory, thermodynamics, all the many things a modern soul theorist must know. Nahum pronounces Macdougall's experiment "silly." He says you'd need not just a scale, but a completely isolated system.

This system — which Nahum would very much like to build — would be a sort of box, a box completely isolated from the surrounding environment. The box sits atop a mind-blowingly sensitive scale, and all around it are arrays of electromagnetic energy detectors. These detectors measure all the different types of known radiant energy (as opposed to informational, or "soul" energy, for which there are no detectors) that might leave the box. Now let's say there's an organism in the box — a paramecium or a wombat or John Tesh, it doesn't matter. And that organism dies inside the box. [iv] If the electromagnetic detectors detect energy leaving the box, there should be a corresponding change in weight. Why? Because of the laws of physics:  there is always a weight loss associated with an energy loss. I'm not talking about the listless feeling that besets the overambitious dieter. I'm talking about E=mc2. If the energy changes, then the mass (which is proportionate to weight) must change — in, you know, a teensy, tiny, infitesimal physics lab way. So if the mass lost when the organism dies is more than what would be expected based on the energy change, then something's leaving the box in a way that can't be accounted for. That something being, perhaps, the soul, or consciousness, heading out to some higher dimension — Lew Hollander's place beyond the open window.

Theorists like Nahum think of the consciousness as information content. And information, to a quantum physicist anyway, has an accepted energy equivalent. And thus a (very very very light) weight. "The change in the heat that has to be liberated per bit of information lost is about three times ten to the minus-twenty-one joules," Nahum says.

I must have made some sort of face. "I'm making this as simple as I can," Nahum says. When you're as brainy as Gerry Nahum is, you lose sight of just how ignorant the rest of us are. Earlier on in our talk, he prefaced the line "Quite a few people look at microtubules as what can be considered almost like an abacus for molecular calculation at a subcellular level" with the phrase "As I'm sure you're aware."

For the sake of not completely derailing the explanation, we're going to accept that the energy lost when one unit of consciousness information is destroyed has been determined by pedigreed physicists to be three times ten to the minus-twenty-one joules, and let Dr. Nahum continue. "And if you use the mass-energy equivalent equation" — the Einstein thing — "then you can say,

Well, if that's true, then that has to represent three times ten to the minus-thirty-eight kilograms.'" So the weight of one bit — the basic unit of information, the stuff that makes up human consciousness — is a billionth billionth billionth of a billionth of a kilogram. "It's very small," says Nahum, and that I understand.

But how many bits are there in a consciousness? Or in one thought? When I think to myself, Is this man blowing smoke up my microtubules, how many bits are involved? Not known. "Is a thought one billion bits?" says Nahum. "Ten billion? We don't know. When we look at consciousness, what is embodied in that? How many bits? We don't know." In a way, it doesn't matter. What's important for our does-the-soul-exist purposes is that changes can be detected:  the energy loss created by a soul heading out the window can, in theory, be detected as a weight loss.

The Fairbanks company does not make a scale for Gerry Nahum's purposes. Does anyone? Possibly. Scales have traveled a surprising distance since Macdougall's day. There are scales that easily and accurately measure micrograms, a microgram being a millionth of a gram. Measuring a billionth of a gram — a nanogram — is also possible, though costly. "What about a picogram?" muses Nahum. That's a trillionth of a gram — ten to the minus-fifteen kilograms. "Can we measure that? Yeah, we can. Remember I gave you the figure ten to the minus-thirty-eight kilograms?" I remember:  in the discussion of the weight of one bit of information. "I've just told you I can measure fifteen orders of magnitude of that. The question is, can I measure the next twenty?" Maybe he doesn't have to. Assuming the consciousness is made up of a vast number of bits, maybe he can get away with the picogram scale.

Nahum says the electromagnetic field arrays around the box are more problematic than the scale. None of these detectors operate over the entire electromagnetic spectrum, so Nahum would have to overlap and improvise. Despite this, he thinks it could be done.

But what if the soul — the residual energy/information that doesn't register on our electromagnetic energy detectors — doesn't go somewhere else, but just, you know, snuffs out? Ceases to exist? That has always been my own pressing, humdrum assumption regarding death.

No can be, says Nahum. Standing in the way is the First Law of Thermodynamics:  Energy is neither created nor destroyed. It has to go somewhere. Nahum says he became convinced that this applied to the consciousness when he was five years old. Around the time you and I were puzzling out the intricacies of the shoelace, Nahum was "thinking about how it had to be conservative, that there's no way out." Nahum swivels to face me. "The question then becomes, Where does it go? The question is not, Is it there? It's there."

We sit quietly for a minute, allowing the guest to absorb this rather dense helping of quantum theory. In a corner of the ceiling, a fluorescent light flickers and goes out. Applying the First Law of Thermodynamics, we know that elsewhere in the universe, an unattractive though cost-efficient glow has just appeared.

Though Gerry Nahum has long been consumed by matters of the soul, he is not a religious man. However, he has had some interesting encounters with the Catholic Church. "I approached them, naively, years ago. To get funding. I outlined it like I just did for you." I picture the bishops in their high-backed chairs, Nahum tucking "Your Eminence" here and there in his warp-speed, single-spaced prose.

The monsignors didn't understand the specifics of Nahum's proposal, but they understood enough to know that it made them nervous. "They have a system of belief where they know what the answer is. They don't need a quote-unquote proof. And if [the results don't] agree with what they know, it's a disaster. They don't want to take that risk." After Nahum's first audience, he was invited back. Now the mood had grown solemn. Outside experts had been called in, theologians with backgrounds in cosmology and physics. Not only did they not offer to fund Nahum's project, they did their best to talk him out of it. They spoke of a "divine design" for the division of the worlds, and tried to make the case that Nahum's experiment threatened a breach of that division. The consequences, they warned, could be dire and unfathomable. "They envisioned that there was a potential for opening a dark 'schism' that might unleash some type of heretofore unknown 'power' into our traditionally protected world." The window metaphor made an appearance. Nahum was accused of trying to "open a window that might not be closed after opening."

But the window presumably opens by itself, whenever something dies. Why would they think Nahum is trying to pry it open? Why would his experiment keep the window from closing? Why can't souls use doors like the rest of us?

At the last meeting, the bishops tried to open a window of the stained-glass variety. "They suggested I might seriously consider converting to Catholicism, so that I'd get over the whole idea. In the end, I had to take a 'just kidding' stance and essentially feign that I had no further interest in pursuing it."


These days, Nahum trolls for funding at physics departments and institutes like the University of Arizona's Human Energy Systems Laboratory. He goes to science-of-consciousness and quantum theory gatherings whenever he can, hoping to hook up with potential partners. It is going slowly. "Most people don't listen nearly as long as you have." Yes, I say, but they probably listen better. Yes and no, replies Nahum:  "It's a multidisciplinary idea, so it's a tough sell. The engineering and information specialist know nothing about biology. The physicians and the biologists and the neuroscientists know nothing about information theory. And none of them know anything about cosmology or … the physics of multidimensional universes. They're very smart people, but they don't have the breadth of background to incorporate it all into one." Nahum is like the discombobulated animals in those children's books where the pages are split into thirds and the ostrich has a kangaroo's legs and the hippo's part giraffe. He's a little of everything, and there's no one for him to play with.

The closest he's come to a soul mate is Patrick Lui, who manages R&D collaborations at the Stanford Linear Accelerator Center and studied thermodynamics in graduate school. I spoke to Lui after I got back from Duke. Lui told me he tried to get other physicists at Stanford, including the former chair of theoretical physics, to "think along with Gerry." Both Lui and his colleagues felt that although the concepts were valid and the project made sense intellectually, the experiment would be difficult or even impossible because of the challenges of measuring such extremely small amounts of energy. "That doesn't mean that one should not pursue this kind of work," Lui was quick to add. "This is a curveball, but nonetheless it is a real ball."

Nahum's idea is also a tough sell among nonacademics. Because, as he puts it, "People either think they already know the answer and don't want any external validation, or they think it's impossible to know the answer. They don't have enough of a background to understand that they can know."

And then there are budget constraints. Nahum estimates he'd need at least $100,000 in funding. "People have said to me, 'We're going to take this up the ladder, see what we can do.' But it's not a mainstream, high-priority enough idea that anyone says, 'Here, let's commit the money.'"

What about the physics department here at Duke? "I get blank stares."

I begin to feel sad for this misunderstood man with his grand and misunderstood — or just not understood — vision.

"Does your wife understand your project?"


"Ex-wife. Not even a little."

Nahum takes a phone call from a business partner named Al. "You're wrong, Al!" he is yelling good-naturedly into the phone. "Al … AL! You're all wet, Al!"

I put away my gauzy pastoral of the lonely philosopher. Gerry Nahum is a tall, charming, pedigreed gynecologist with healthy self-esteem. One day he'll get the support he needs to carry out his plan, and possibly the respect of the Duke physicists, and maybe even a wife who knows quantum theory. I hope so.


It is 2 p.m. before Nahum's stomach makes itself heard over his brain and we break for lunch. With the equations put away and at least a few picograms of Nahum's informational content devoted to his ravioli, I feel more comfortable asking the dimwit questions I've wanted to ask all morning.

What do you think it would feel like to be a free-floating soul, a far off energy in some god-knows-where-or-what dimension? Nahum makes the analogy of the computer:  Your basic core of consciousness, he imagines, would be like the operating system. On top of that you have various overlays:  word processing and spreadsheet programs and such if you're a computer; if you're a human being, perception, language, reason, memory. When you die and the brain shuts down, the overlays fritz out. You're left with the operating system:  a sort of primitive, free-floating awareness. Nahum imagines existence would be "like what it is for us now, minus all the superficial trappings."

It's that minus-all-the-trappings bit that gets me. If you can't think in words of see or hear, what are you like? Coma victim? Lichen. Nahum shrugs. It's just an analogy, just a guess. I posed this question to Lui later in the week. He was dubious about the possibility of the information content of a person's consciousness leaving the body in any sort of organized form. "Decay heat is not ordered information," he said. Meaning, I think, that the chuck of energy that was your personality may indeed continue to exist after you die, but not in the form of your personality. Not in the form of something you can be or use.

I later relayed to Nahum what Lui said and asked him to comment. "Remember," I wrote, "in replying to me, pretend you are talking to a seventh-grader." Nahum disagreed with Lui. His reply ran to a thousand words and would have been understandable to any seventh-grader familiar with Kant, Locke, negentropy as the measure of nonrandomness, and the Enigma encryption machine. Here is the part I understood:  "This energy is freely malleable in terms of the physical form it might take … and it is not necessarily the case that any one of them would be 'preferred.'"

Well, "preferred" in the sense that it would be more fun to be a spirit that can think thoughts and remember memories than to be, say, a black hole or a piece of static electricity. But I decided to leave it be. 


Nahum orders bananas Napoleon for dessert, just one more way we'll never understand each other. We're back to talking about the box, the system. I realize I forgot to ask him what kind of organism he's planning to put inside. The dessert arrives, a massive custard download held vertical by wafer shelving.

"So what goes in it?" I'd been assuming a lab mouse.

"Banana pudding, mostly."

When I get back home and I look at Nahum's twenty-five-page "proposal for Testing the Energetics of Consciousness and Its Physical Foundation," I will picture a plate of banana pudding in a box.

Theoretically, Nahum could sacrifice anything from a bacterium on up. He is leaning toward leeches. "I worked with leeches for a long time. They're slimy and they latch on to you. They're a very awful organism. I hated those things!" The couple at the table beside us turn to look at the man who hates leeches.

Last question:  What does he think the result will be? Does free-floating consciousness energy exist? "My bias is that it does exist," says Nahum. "But I would never say that I know that." He puts down his spoon. "Until I prove it."


[i] Medical treatises were eminently more readable in Sanctorius's day. Medicina statica delves fearlessly into subjects of unprecedented medical eccentricity:  "Cucumbers, how prejudicial," "Phlebotomy, why best in Autumn," and the tantalizing "Leaping, its consequences." There's even a full-page, near-infomercial-quality plug for something called the Flesh-Brush.

[ii] Astoundingly, Sanctorius was described as a small man. His work habits may explain his ability to stay slim in an era of eight-pound dinners. He claimed to have tested 10,000 subjects in 25 years.

[iii] That is to say, at the time I visited him. He has since left Duke and works for the Food and Drug Administration in Rockville, Maryland.

[iv] Credit for the original seal-a-soul-in-a-box experimental format must go to Frederick II, the thirteenth-century King of Sicily and Emperor of the Holy Roman Empire. In the diaries of the king's sometime chronicler, the Franciscan monk Salimbeane, there is a description of Frederick shutting up "a man alive in a cask until he died therein, wishing thereby to show that the soul perished utterly." Though Frederick is to be credited for his precocious enthusiasm for scientific method, the cruelty of his experiments invariably outweighed their scientific merit. To wit, the time he "fed two men most excellently at dinner, one of whom he sent forthwith to sleep, and the other to hunt; and that same evening he caused them to be disemboweled in his presence, wishing to know which had digested the better" (the sleeper). At least that one makes some sense.

Reprinted from Spook, by Mary Roach. © Mary Roach. Published by arrangement with Norton.

Original art courtesy Rob Grom.

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Articles in this Issue

A Soul's Weight, by Mary Roach
Know Me Now, by Steve Lohse
Veterans, by Tom Bissell
A Field of Trees and Bones, by Kate Pickert
Circum-schism, by Grant Stoddard
Nutrition, by Benjamin Hart
Hospitality and Tourism, by Peter Olszewski
Horticulture, by Kathryn Small
Penmanship, by Jeff Steinbrink
Economics, by Robert Sullivan


Mary Roach is the author of Stiff and Spook. Her writing has appeared in Salon, Wired, Outside, GQ, Discover, Vogue, and The New York Times Magazine. She lives in Oakland, California.

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