Pasteur, Koch, and Germs Part 1: Seeds vs. Soil

Alright, so Jenner ushered in a strange chapter of medical history, but surely medicine became more objective after that point, right? This was just an embarrassing medical fluke, right? The original vaccine didn’t help at all, but we have different vaccines today based on better understanding and new technology, right? Vaccines must have gotten more effective after Jenner, right? These questions bring us to late nineteenth century France and Prussia.

Note that nowhere in the previous section on smallpox have germs been mentioned¹. This was because of the historical reality of the time: Something like germ theory had existed in some form basically forever, but in Jenner’s time it was not yet the universally believed theory that it is today. Even in the early days of smallpox vaccination, people would speak of the “virus” of a disease, but this word didn’t yet have its modern meaning. Virus is actually the Latin word for poison, and originally that’s what the word meant—it originally had nothing to do with the ultramicroscopic intracellular parasites that we’re all familiar with today. It was left open what exactly the poison was made of, and Jenner didn’t concern himself much with it, except briefly to speculate that it came from horses.

But the popularity of germ theory was surging in the decades leading up to Pasteur’s day, and he both learned about it and then became its most famous promoter. In the same way that Jenner wasn’t the first to imagine that cowpox prevented smallpox, Pasteur was far from the first to imagine that invisibly small creatures would pass from person to person causing disease. Pasteur became a popularizer of the germ theory, which is actually a very ancient belief. Let’s therefore go over some of the names of the people who put forward germ theories of disease throughout history.

In the first century bc, the Roman Atomist named Titus Lucretius Carus wrote his famous poem On The Nature of Things, in which he expounded the Atomist worldview, including germ theory, and which would prove very inspiring to later germ theorists. The following is a portion of Book 6 of the poem, as translated by William Ellery Leonard.

This do I say, as oft I’ve said before:

In earth are atoms of things of every sort;

And know, these all thus rise from out the earth-

Many life-giving which be good for food,

And many which can generate disease

And hasten death, O many primal seeds

Of many things in many modes- since earth

Contains them mingled and gives forth discrete.

And we have shown before that certain things

Be unto certain creatures suited more

For ends of life, by virtue of a nature,

A texture, and primordial shapes, unlike

For kinds alike. Then too ’tis thine to see

How many things oppressive be and foul

To man, and to sensation most malign:

Many meander miserably through ears;

Many in-wind athrough the nostrils too,

Malign and harsh when mortal draws a breath;

Of not a few must one avoid the touch;

Of not a few must one escape the sight;

And some there be all loathsome to the taste;

And many, besides, relax the languid limbs

Along the frame, and undermine the soul

In its abodes within. To certain trees

There hath been given so dolorous a shade

That often they gender achings of the head,

If one but be beneath, outstretched on the sward.

There is, again, on Helicon’s high hills

A tree that’s wont to kill a man outright

By fetid odour of its very flower.

And when the pungent stench of the night-lamp,

Extinguished but a moment since, assails

The nostrils, then and there it puts to sleep

A man afflicted with the falling sickness

And foamings at the mouth.

Lucretius, writing in Latin, believed in primal entities that would enter into a person’s eyes, ears, nostrils, mouth, or skin and “generate disease, hasten death.”²

Vivian Nutton’s 1983 paper The Seeds of Disease: An Explanation of Contagion and Infection from the Greeks to the Renaissance goes on to speculate about where the theory of germs came from, saying, “It is possible that the idea of seeds of disease goes back to Epicurus (341–271 bc) or even to the Pre-Socratic atomists Democritus and Leucippus, or it could have been first formulated or developed by a slightly later authority.” It’s speculated that this is the case because it’s not believed that Lucretius was very much an originator of ideas as much as a propagator of the ideas of earlier Atomists like Leucippus, Democritus, and Epicurus. He was someone who repeated what others said before him, except through the medium of poetry. Today, he might be called a “science communicator.” Therefore, in speculating that the germ theory went back to Leucippus or Democritus (the originators of Atomism) or Epicurus (a later Atomist), Nutton was suggesting that germ theory might have been one of the doctrines of the original Atomists, or perhaps a doctrine of some later Atomists, and that it was merely being repeated and propagated by Lucretius.

Nutton’s hypothesis is supported by the writings of Plutarch, an important first-century historian and priest of Apollo, who described the different medical schools of thought that existed in his day. In particular, there was an Atomist named Philo of Hyampolis living around the first century who believed that seeds of disease could rain down to earth from other worlds³. Nutton comments, “Both Plutarch and Diogenianus thus favoured a typically Hippocratic correlation of disease and bad regimen, and rejected the arguments of Philo the Democritean Methodist for causative seeds, atoms, or first principles.” Therefore it seems that germ theory was a doctrine belonging to the Atomists.

Twenty years after Lucretius wrote about it, a Roman polymath named Marcus Terentius Varro gave a description of the germ theory, saying,

Precautions must also be taken in the neighbourhood of swamps, both for the reasons given, and because there are bred certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there cause serious diseases.

This is from a 1934 translation of Book 1, Chapter 12 of Varro’s work On Farming. It could be argued that Lucretius was vague in that he only spoke about certain “forms” that cause disease (Latin figuras), but here in Varro’s writing it’s explicitly small creatures that caused disease (Latin animalia quaedam minuta, quae non possunt oculi consequi). The idea could have been more ancient than this, but this book from 37 bc is at least the earliest, unambigious, surviving record of the belief that microbes cause disease.

It’s interesting to reflect on how Varro could possibly have known about invisibly small disease-causing creatures given the lack of microscope technology that existed in his time: It would have been impossible for him, his contemporaries, or his predecessors to have any experimental evidence for this hypothesis. This is to say that this kind of thing could only have been a belief he held on faith, not a belief held because of evidence. This also just goes to show how truly ancient the doctrine of germ theory really is. The germ theory has existed for thousands of years. This obviously means that Pasteur didn’t come up with it.

A couple centuries after Varro and Lucretius, in the late second century, the famous Anatolian physician Galen – probably only second to Hippocrates in influence over the history of western medicine – recycled the metaphor used by Lucretius that there might be “seeds of disease,” echoing the sentiment of Lucretius, Varro, and Philo. Nutton pointed out that, “The aptness of the seed analogy lies in the fact that it emphasizes three things: that the object posited is a living entity; that it is in origin very small; and that it contains within itself the potential for growth.” Nutton went on:

Galen nowhere explained the transmissibility of the skin diseases, but he argued that plagues were spread by the inspiration [i.e. inhaling] of air already infected by a “putrid exhalation” (ὑpò shpedonẃdous ἀnajumiásews mianjéntos) – witness the deadly rotten air from corpses left unburnt after battle, the exhalations from swamps and pools in summer, and the hot pestilential atmosphere described by Thucydides during the great plague of Athens of 429 bc.

So Galen already was talking about “seeds of disease” and diseases passing from one person to another when one person inhales another’s putrid exhalation.

Writing in the early seventh century, Isidore of Seville gave an etymology of the Latin word contagium, from which we get our word “contagion.” He said that it came from the Latin verb contingere, a compound word being composed of the prefix con, meaning “together,” and the verb tangere, meaning “to touch.” (Our word “contact” also happens to come from these exact two Latin words.) Isidore believed the plague to be contagious, and one of the hypotheses he entertained regarding its contagiousness was that of “plague-bearing seeds” (Latin pestifera semina rerum).

Talk about “seeds of disease” was almost nonexistent in the Middle Ages, except for in the works of Dino del Garbo and his son Tommaso del Garbo, who, in the fourteenth century, mentioned in passing that Galen spoke of “seeds of plague.” Tomasso’s commentary was published in 1345, a single year before the famous Black Death plague epidemic broke out, and it was a very influential text, influential enough that it was being copied and then printed even into the sixteenth century. Therefore Tomasso’s statement about “seeds of plague” certainly had an influence over how medical professionals in the following centuries thought about plague.

It should be pointed out that, by the Late Middle Ages, many texts from classical antiquity had been lost or were forgotten, including pretty much all of the writings of the Atomists—most of which are still lost to this day. The Renaissance began when Italian humanists scoured European libraries for antique manuscripts on the verge of being lost, millennium-old documents almost falling apart at the touch and guarded in old, isolated monasteries⁴. Those Italian humanists found Latin copies of the writings of ancient men like Cicero, Livy, and Seneca. In the year 1417, a copy of On the Nature of Things by Lucretius was tracked down and discovered by Poggio Bracciolini. That document was brought to Florence and copies were made of it by Niccolò de’ Niccoli for the sake of its preservation and distribution. Already in 1473, that ancient poem by Lucretius was being printed.

With Lucretius being mass-produced for the first time, the Renaissance marked the beginning of an Atomist revival. Inspired directly by Lucretius, it was a Venetian Atomist named Girolamo Fracastoro whose 1546 book On Contagion and Contagious Diseases sought to explain disease in terms of invisibly small, rapidly multiplying creatures that passed from person to person, either by direct contact, by contact with intermediate surfaces, or at a distance⁵.

It should (again) be emphasized that, since microscope technology didn’t exist before about the seventeenth century, everyone who supported the germ theory before this point must have had some strange devotion to the theory for reasons other than evidence. Therefore the theory’s true believers held to it so moreso out of religious conviction than out of a scientific attitude and an appreciation for evidence. There was not evidence—and yet the theory found many devotees carrying the torch from antiquity, including Fracastoro. But it was around this point in the history of medicine that microscopes were invented and being improved, so it would only have been at this point that germ theories could actually start to become testable.

In August of 1674, the Dutch microscopist Antonie van Leeuwenhoek pointed a microscope of his own design at water from a lake named Berkelse Meer and saw certain little creatures swimming around. For this he’s become universally regarded as the so-called “father of microbiology.” Very interestingly, the ancients were right after all: There really were certain minute creatures that the eyes can’t perceive. If evidence could be put forth that at least some of these creatures can cause disease, then the ancient germ theory could be proven. Given the rise in popularity of Atomism, especially because of the rediscovery of Lucretius, it would make sense if many people were anticipating that this evidence would be forthcoming.

Fracastoro worked at the University of Padua, an important center of medical research and the intellectual home of Fracastoro’s contemporary Andreas Vesalius, who wrote the most influential books on anatomy. Evidently the germ theory was kept alive and well there because almost two centuries after Fracastoro’s book, and a few decades after Leeuwenhoek’s discovery, in 1714, Carlo Francesco Cogrossi, a Cremish physician who studied medicine at Padua, hypothesized that a certain disease in cattle was the result of a germ. At Padua, Cogrossi went on to teach medicine to Marko Anton von Plenčič, a Slovenian physician. Plenčič would be regarded as one of the foremost germ theory promoters of his day for suggesting that every disease was the result of germs causing havoc in the body. This was the topic of his 1762 book, and this happens to be the essence of the germ theory often attributed to Pasteur, except more than a hundred years prior to Pasteur’s writings on the subject.

Then in the next century, there was the smallpox vaccine disaster. As evidence that at least the belief in contagion was on the rise, it was documented in the previous section that compulsory vaccination started because of a belief that non-vaccinated people could spread smallpox to the vaccinated, but this obviously implies at least a belief in contagion, i.e. disease passing from one person to another. Moreover, in her 1860 book Notes on Nursing, the famous British nurse Florence Nightingale had also described being taught that smallpox was something contagious, passing from person to person⁶.

Pasteur’s son-in-law, René Vallery-Radot, would go on to write a biography of Pasteur, and in it Vallery-Radot even stated that, “The ancient medical theory of parasites and living contagia was revived.” Again, that’s from the biography of Pasteur written by his own son-in-law. If Pasteur had been its originator, then there wouldn’t be so much evidence of the existence of germ theory predating Pasteur’s work on the subject, and even his own son-in-law calling it an “ancient medical theory.” So regardless of where the germ theory of disease really came from, we can be certain that it didn’t have its origin with Pasteur. These were truly ancient concepts passed down for thousands of years.

Pasteur had already been a proponent of the germ theory of fermentation and the germ theory of putrefaction, but he held off from writing about the germ theory of disease for a while. But in 1875, which was three years before Pasteur would first come to publish on the topic of the germ theory of disease, H. Charlton Bastian published a paper titled The Germ-Theory of Disease: Being a Discussion of the Relation of Bacteria and Allied Organisms to Virulent Inflammations and Specific Contagious Fevers. According to Bastian,

The subject of the relation of the lower organisms to disease has, moreover, a growing importance. The notion that there is a distinct causal relation between the two—though it has long existed in one form of another—is one which has been spread enormously within the last few years, partly owing to our increase of knowledge concerning these low organisms, and partly because of their ascertained presence in numerous diseased tissues and exudations.

Bastian went on to say that a person affected by a contagious disease “throws off particles from the region specially affected, or from many parts of the body; and these particles, on coming into contact with suitable surfaces in other persons, may incite similar local or general diseases—though such results do not invariably follow.”

It should also be pointed out that it wasn’t just the germ theory of disease that had been believed by the ancients, but also the germ theory of fermentation. It appears that there had long been a general belief in the connection between fermentation and disease. The English philosopher, chemist, and theologian Robert Boyle made a comment about how anyone who understands fermentation will be able to understand contagious diseases. The alleged connection between fermentation and disease appears to have been taken very seriously, since, starting in the mid-nineteenth century, the term “zymotic” was used for certain diseases believed to be contagious, coming from the Greek word zumoun, transliterated zymoun, which was the verb meaning “to ferment.” But then with the mysteries of fermentation having been solved and attributed to microbes, it seemed very natural that the zymotic diseases would turn out to be the result of microbes too, further strengthening everyone’s belief in germ theory. If fermentation is caused by microbes, then why wouldn’t contagious diseases be caused by microbes? If microbes can enter into a barrel of grape juice and convert it into wine, then why wouldn’t they also be able to enter into a healthy man and convert him into a diseased man? Since Robert Boyle’s comment was quoted both by Bastian and also by Vallery-Radot, it appears that this sentiment must have been widespread by the late nineteenth century. Moreover, in his previously quoted 1875 paper, Bastian actually questioned whether scientists and medical professionals might have been resting too much of their case on the simple analogy between fermentation and infection.

So anyone who credits the germ theory of disease to Pasteur hasn’t actually investigated the matter at all. Over and over again, there have been people promoting the germ theory, even including some not mentioned here. But there is a reason that Pasteur’s name stands out above the others: The reason that people like Epicurus, Lucretius, Varro, Fracastoro, and Plenčič aren’t typically credited with germ theory is because they lived in a time when germ theory really was still just pure speculation, taken on faith alone. There was absolutely no evidence whatsoever to support it. But since Pasteur was a microbiologist, and since the germ theory of disease was becoming increasingly popular to talk about, Pasteur was in the perfect position to come along and actually supply the evidence that the ancients couldn’t. This is what’s supposed to set Pasteur apart.

Of course, it’s an enormous red flag that – for thousands of years – the germ theory has had believers despite a total lack of evidence. Since people were happy to believe it without any evidence for thousands of years, then we really need to check ourselves: Has the evidence finally been supplied after all, or have people merely continued taking some ancient belief on faith? Do we have evidence that diseases are caused by germs after all, or have we merely inherited a zeal for Atomism? These might sound like crazy questions, but because it makes sense to ask these questions, it only makes sense to seek out the evidence for the germ theory and make sure that the evidence really is out there. We need to see that the empirical work of Pasteur and his followers holds up to scrutiny. If we don’t check ourselves, we risk being fooled into believing something merely because it’s been passed down to us. We have to be curious, skeptical, and open-minded.

But before we begin to examine the work of Pasteur and the rest to make sure that they really did prove all the things they claimed to prove, it makes sense to make some comments about germ theory’s biggest competitor, at least for the sake drawing a comparison. Being aware of this alternative to the germ theory will allow us to think about whether people really have ruled out the alternatives to the germ theory, or if we’re all just believing that microbes are germs without evidence.

The little-known alternative to the germ theory usually goes by the name of terrain theory⁷. Terrain theorists will typically attempt to locate the primary cause of a particular disease either in a toxicity or in a nutrient deficiency rather than in a particular microbe. For example, Richard Holland’s 1728 explanation for smallpox is a terrain perspective in which some kind of toxic exposure came first and then what we call smallpox is the body’s response to that toxic exposure, in fact even a healing response. While Alfred Russel Wallace certainly believed in contagion, his explanation as to the cause of smallpox (and the rest of the “filth diseases”) was certainly more in line with terrain theory than with germ theory. Moreover, Florence Nightingale’s own interpretation of her experiences is even totally inconsistent with germ theory—but very congruent with terrain theory.

Moreover, it’s crucial that the reader understand that it’s very common to use terrain theory, even if we don’t explicitly mention the theory by that name. All the diseases covered in the first sections of this chapter seem to better be described by terrain theory than by germ theory. Cancer, heart disease, stroke, and type 2 diabetes are all leading killers, and yet they are not infectious diseases caused by germs spreading from person to person; they’re lifestyle diseases, i.e. diseases resulting from a person not taking proper care of his “terrain.” Moreover, it doesn’t matter if we blame cardiovascular disease on seed oils, fluoride, pharmaceuticals, etc., or if we blame it on saturated fat, cholesterol, red meat, etc., since both of these are terrain perspectives. The primary causes of cardiovascular disease seems to be the consumption of certain toxins rather than the invasion by certain microbes, and that holds true both for the mainstream perspective as well as for the alternative perspectives. Moreover, the symptoms of fluoride toxicity are the result of consuming fluoride, not the result of an invasion by a disease germ; mercury toxicity is the result of consuming mercury and has nothing to do with germs. We could include other well-known toxic assaults as well: For example, when someone drinks a lot of vodka and feels terrible the next day, he doesn’t say, “There must have been a germ in that vodka I drank.” That would be silly. He knows that the way he feels was the result of how that vodka per se affected his body—no germ involved. A hangover is a disease explained by terrain theory, not by germ theory. Nutrition and toxicology are branches of biology and medicine that use a terrain perspective, even if this word “terrain” isn’t usually explicitly used. So at this point, while it might be plausible that germ theory could explain certain diseases, it must be admitted that terrain theory is already at least a better explanation for certain other diseases, and that we already use terrain theory to explain diseases like heart disease.

Since terrain theory is all about nutrition and toxicology, the reader might be curious about what role microbes play in this theory. Proponents of terrain theory simply point out that a proliferation of microbes might accompany a disease, but that that doesn’t automatically mean that they’re the causative agent (to assume so would be to fall for the cum hoc, ergo propter hoc fallacy). Instead, terrain theorists point out that something else might have affected the body’s “terrain” such that these microbes were called into action, to help neutralize poisons and break down diseased tissue. This is to say that this alternative perspective holds that, rather than acting as parasites on us, microbes have a “saprophytic” effect, essentially acting as “nature’s clean-up crew,” or even a “bioremedial” effect, helping the body to heal. In this view, microbes aren’t causing diseases in tissues, but rather helping to break down tissue that was already dead or diseased for some other reason.

For example, a smoker might damage his lungs in a certain way through the act of smoking mass-produced, low-quality cigarettes that are loaded with pesticides and other strange chemicals; in response to this, he might come down with some kind of lung disease. Upon his death, an autopsy might reveal an infestation of the bacterium Mycobacterium tuberculosis. The germ theorist might say, “Ah ha!” and think that it was the bacterium causing him his sickness, but it must be admitted that it might have been the smoking per se that was damaging to his lungs and causing sickness, with these bacteria only attempting to break down the poisons and dying tissue after the fact, poisons and dying tissue which were themselves really the results of smoking strange chemicals. Since we don’t have any a priori way to say one way or the other whether the bacteria were helping or hurting the person with lung disease, we must turn to empirical methods. That’s the entire point of experiment: discerning the nature of causality. It shouldn’t be controversial to say that we need experiments for determining causal relations. Careful experiments must be conducted that allow us to know whether a certain bacterium is the cause of disease or merely at the scene of the crime. If we skip over experiments and just assert that the bacterium is the cause, then we’ve abandoned empiricism in favor of simply assuming the conclusion. And if it’s the case that such experiments haven’t been done, then we would have to admit that there would be no empirical evidence that the smoker’s tuberculosis was caused by a bacterial invasion. This can be generalized to any disease believed to be caused by a microbe: If sufficiently rigorous experiments haven’t been conducted to show that the microbes play, beyond any doubt, a causal role in the etiology of a particular disease, then we can’t say that there’s evidence of the germ theory of that particular disease. Without those experiments, there would be no reason for holding a belief that a certain microbe causes a certain disease.

Moreover, it shouldn’t be a surprise that a bacterium associated with a disease might merely be breaking down toxins and dead tissue rather than causing disease: We’re already familiar with the fact that microbes (and other creatures) do this in nature. When an animal dies in the woods, and its body is broken down by maggots, fungus, and microbes, no one would think that the maggots, fungus, and microbes are what killed the animal; everyone would recognize that they showed up after it died to break down its remains, making them usable again. In the same way, it’s at least very plausible that proliferating microbes in the body of a diseased person might actually be a part of the recycling process, breaking down toxins and turning decaying tissue into usable materials again, and only coming along after something else already went wrong. And since pretty much everyone accepts that our gut microbes are necessary for helping us digest food, we could also wonder if the proliferating microbes even play a role in the healing process. If they can help us digest, why couldn’t they help the body heal too?

Robert Koch, the late nineteenth century Prussian bacteriologist, second only to Pasteur in repopularizing the germ theory of disease by introducing empiricism, designed a rigorous experimental procedure which is intuitive to anyone who comprehends the basics of experiment and germ theory. This list of four steps is supposed to demonstrate unambiguously that a particular microbe really is a disease germ, rather than just a microbe associated with a disease. The steps of this procedure have come to be named after him, being called Koch’s postulates. They are as follows:

1. If a microbe is the cause of a given disease, then the microbe should be found in abundance in the diseased tissue of all creatures with that particular disease. If there are creatures with the disease that don’t have the suspect microbe, then obviously the microbe can’t be the cause of their disease. Moreover, it should generally be absent in healthy individuals, although germ theorists have historically explained this away by invoking an immune system to explain why healthy people and animals can have disease germs.

2. Having found a microbe that satisfies the first postulate, it should be cultured and separated from everything else. This second step is known as isolation or purification. The reason this step is so crucial is because the suspect microbe can only be used as the independent variable in an experiment if it’s first been separated from everything else.

   As an aside, the word “isolated” comes from the Italian word isolato, which is derived from the Latin insulatus, both of which mean “made into an island.” In the same way that an island is, by definition, separated from all other land, when a microbe is isolated, it means that it must be separated from everything else. This is obviously the only way that the term “isolated” could have originally been meant with respect to proving that a microbe is a disease germ since only getting the microbe all by itself would allow for it to be used as an independent variable in the experiment.

3. Having isolated the microbe suspect, it should be introduced to a healthy creature, and if this microbe is the cause of a particular disease, then the creature should come down with that specific disease, i.e. not some other disease.

4. Having caused disease in a healthy creature using a microbe, the microbe should then be found in abundance in the now-diseased creature, and it should be the same microbe that was originally found, cultured, and isolated⁸.

It should be obvious to anyone that if this procedure can be repeatedly done for a given disease, then there is at least a very good reason to believe that the microbe found is a disease germ responsible for causing that particular disease. This procedure is based on nothing more than a logical understanding of the claims made by germ theory. And since this procedure should be easy and repeatable if a disease really is caused by a germ, then if this process is not repeatable – or not even possible – then, on the contrary, we must be suspicious that there is no germ causing the disease. If that’s the case, it might instead be beneficial to look for alternative explanations. It’s when everyone believes that a disease is caused by a germ and this process fails that we might have to abandon a previously held germ-theoretic understanding of a given disease.

Koch’s postulates help to determine beyond all doubt that the microbes are the cause of disease. Whenever dealing with issues of causality, a common analogy is often made to firefighters: Just because firefighters can almost always be found at the scene of a house fire, that doesn’t mean that they’re the one’s causing house fires; they exist to heroically save the people and property from the fires. But we could see if firefighters do cause fires by carrying out some version of Koch’s postulates on them: Having observed firefighters at the scene of pretty much all house fires, we could get some firefighters alone, introduce them to houses, and then wait to see if they cause any fires. When they don’t cause any fires, then we’d know for certain that it’s not the firefighters causing fires but rather the fires causing firefighters to appear. This might sound like a silly example, but that’s only because we all already know the role that firefighters play when it comes to house fires; the same isn’t true for microbes and disease. Also, if one always saw firefighters at the scene of house fires and decided to solve the problem of house fires by disbanding all fire squads, that would obviously only make the problem of house fires worse. The causal relationships really have to be understood before interventions based on them can be employed with any degree of confidence, and in the realm of disease that means carrying out Koch’s postulates.

Another point that should be made: There’s no a priori reason to believe either that all diseases need to be explainable in terms of germ theory or that all diseases need to be explainable in terms of terrain theory. Each disease raises its own empirical question as to its etiology. In principle, it’s perfectly possible that some diseases are caused by toxic exposures, others are caused by malnutrition, and others are caused by invasion by germs, and it shouldn’t be at all controversial to say that. Even Louis Pasteur himself is recorded describing at least one disease using terrain theory⁹, which is pretty awkward for the people who both worship Pasteur and also want to say that every single disease without any exception is caused by germs. We just need to be certain that Koch’s postulates have been carried out to know that we have a justified belief in the germ theory of any particular disease. It’s as simple as that.

This all needs to be emphasized because some people like to make the claim that terrain theory is “pseudoscientific.” Of course, anyone who makes such a claim is actually making a couple extremely bold claims that anyone could recognize as utterly ridiculous. First of all, such a person is saying that every single disease – without any exception – is caused by a germ. (I’d love to see his proof of the existence of a hangover-causing germ. Are hangovers contagious now too?) Moreover, to dismiss terrain theory is to deny that deficiencies and toxicities can ever be the primary cause of disease. After all, every disease being caused by a germ would obviously exclude all nutritional and toxicological explanations for disease that don’t make reference to a microbe. So to say that terrain theory is pseudoscientific is essentially to say that nutrition and toxicology are pseudoscientific. Whether he understands it or not, he’s claiming that diseases like like heart disease, mercury poisoning, and hangovers are caused by germs, which is obviously nonsense. To slander terrain theory as “pseudoscience” is to claim that asbestos can’t cause cancer, simply because it’s a mineral and not a microbe. The only options are to admit that there are at least some diseases that terrain theory is better at describing or to make oneself look silly by doubling-down and just asserting that diseases that result from nutrient deficiencies and toxicities must really be caused by unidentified germs, despite a total lack of evidence. That’s quite the bullet to be biting.

Moreover, it’s actually fairly common that a disease previously thought to be caused by a germ ends up being better explained by changes of terrain. The classic example of this is scurvy, which we today recognize as a deficiency rectified by the consumption of certain foods, most notably citrus fruits. But one can imagine that if sailors were at sea for long periods of time, with one person after another coming down with scurvy on an isolated ship (with many of them dying), it might look like the scurvy is passing from one person to another, and fear¹⁰ might make the sailors jump to conclusions. If a first sailor shows symptoms of scurvy, and then a second sailor shows symptoms shortly after, the crew might imagine that a disease germ must have jumped from the first to the second. And indeed, this is what was believed for a long time. In reality, it was just that they were all consuming diets that were deficient in certain foods¹¹. Scurvy is therefore today recognized to be not the disease of a germ, but a disease of the terrain, even though it was originally thought to be contagious. Just like scurvy, cancer was similarly initially thought to be caused by a germ. Émil Grubbé, the inventor of radiation therapy, even suggested that radiation therapy worked by killing cancer germs with radiation. Now cancers are typically believed to be caused by toxic exposures (a terrain perspective) or random mutations (a genetic perspective), although there is a lingering belief that certain cancers can be caused by germs.

Other diseases thought to have been contagious include beriberi, which is supposed to be the result of a vitamin B₁ deficiency, and pellagra, which is supposed to be the result of a vitamin B₃ deficiency. Samantha and Mark Bailey report on beriberi as follows:

Beriberi was described at least as far back as 600AD in traditional Chinese medicine scripts. Chinese practitioners knew the condition would be deadly and had recognized that certain foods were useful in its treatment. In more modern times Japanese naval physician Takaki Kanehiro was tasked with investigating beriberi in the 1880s due to the heavy toll the disease was taken on seamen during long voyages. He discovered that increasing the amount of barley, meat, milk and vegetables reduced the number of cases dramatically. However, his remarkable discovery was ignored because of the prevailing belief amongst the establishment of doctors of the time that it was an infectious disease.

Their book also goes a bit into the history of pellagra, and how it was known at least as early as 1735 to be caused by malnutrition. Nevertheless, that old knowledge from centuries ago was lost and had to be learned the hard way all over again when people tricked themselves into thinking that it was a contagious disease.

The fact that pellagra was already known to be a nutritional problem makes it all the more embarrassing for “modern medicine” that, in 1912, a professor of pathology named Guido Tizzoni claimed to have isolated a pellagra-causing microbe. These were not contagious diseases, but, because people had already committed themselves to the belief that they were contagious, the media was able to stoke fear in people who were terrified of “catching” these deficiencies from their neighbors. Daniel Roytas described the fear of contagious pellagra, which was in all likelihood stoked by Tizzoni’s “discovery,” saying,

People were so fearful of catching pellagra that a wave of ‘pellagra-phobia’ swept across the United States in the early 1900s. Many hospitals refused to admit pellagrins, and it was not uncommon for nursing staff to refuse treatment for those admitted with the affliction. Some nurses even went on strike after being instructed to treat pellagra patients for fear of being infected themselves. Quarantine measures were implemented by hospital staff in the hope of reducing transmission of the disease, but all to no avail. Elementary schools barred children from school grounds if any of their family members were ill, while hotel patrons threatened to leave en masse if guests displaying even the mildest pellagra symptoms were not promptly vacated from the premises.

To the people who believed in contagion, the fear of “catching” these nutritional problems was very real.

And, of course, if it’s falsely believed that a disease is caused by a microbe invader, then the obvious “solution” will be to consume poisons aimed at killing the unwelcome intruder. Poisonous substances were therefore given to people who had these nutritional deficiencies, and the physicians administering these poisons assured everyone of their effectiveness. The Baileys point to one physician who, also in 1912, claimed that there was a “decidedly favorable effect” when he gave his pellagra patients arsenic. Roytas found a different physician making the same claim about arsenic, with the treatment going on until the 1930s. Roytas also found another physician who recommended bichloride of mercury for the condition.

We could also imagine an almost silly hypothetical to demonstrate this point about how the same condition might be explained either in terms of germs or in terms of terrain: Imagine a universe in which people don’t understand what causes dry lips. In this hypothetical universe, people might notice that lots of people get try lips each year in the winter months. A terrain theorist might notice that, because it pretty much only happens seasonally, the disease might have a seasonal cause as well. He might expect that there might be some seasonal change in people’s terrain that leads to them having the disease that is dry lips. The terrain theorist might hypothesize that exposing the lips to air that’s both cold and dry might result in dry lips. If everyone is exposed to cold, dry air seasonally, then the seasonality of dry lips makes sense. A germ theorist on the other hand might see a person “catch” dry lips after being in contact with some other person who had dry lips, and therefore imagine that something was physically transmitted from one to the other, just as sailors used to imagine scurvy passing from one person to another. He might hypothesize a germ that jumps from person to person through the air, causing dry lips wherever it goes. Seasonality doesn’t make a whole lot of sense from a germ theoretic perspective, so he might try to explain this evidence away in a rather ad hoc fashion by postulating an “immune system” which is seasonally weakened, particularly in the winter months. In his empirical studies, he might find a microbe that’s usually present on the lips of people with dry lips and usually not present on the lips of people without dry lips, (prematurely) declaring it to be the germ that causes this condition, without actually carrying out Koch’s postulates. (He might not even question whether that microbe is there to recycle the dead tissue on a person’s dry lips, and therefore serve a beneficial purpose, even though the terrain theorist would be interested in asking such a question.) He would probably give this microbe a fancy sounding name involving roots from at least one ancient language, a name such as Desiccolabrum aridus, which would mystify those people not familiar with Latin. We could then imagine people rubbing poisons on their dry lips in an attempt to kill this “germ” and heal their lips. Further, we could imagine people coming up with inoculations against D. aridus, or even mandates for people to be inoculated against it. Children might not be allowed to attend schools without being “immunized” against D. aridus. Of course, in the real world, we understand that cold, dry air is the cause of dry lips (i.e., we all understand that having dry lips is a disease better explained by terrain theory than by germ theory), but in a world where everyone has been taught from a young age to believe in the dry lip germ, it could be very difficult convincing anyone that there is no such thing as a dry lip germ. When the terrain theorist tells them that there is no dry lip germ, they might scoff, saying, “You’re a fool if you don’t believe in dry lips!” misunderstanding that the existence of the condition is not what’s in dispute, but rather the cause of the condition—but of course, when one can only think in terms of germ theory, the microbes and the diseases they’re alleged to cause become almost synonymous, and therefore, in such a hypothetical world, it would be hard for most people to even imagine dry lips not being caused by a dry lip germ. Then if the terrain theorist points out that dry lips are caused by cold, dry air, the germ believer will dismiss his point, citing studies funded by the dry lip vaccine manufacturers—as if completely ignorant of the conflict of interest that those manufacturers have. Moreover, he might take the conclusions of those studies at face value, without even evaluating for himself whether the methodology used had been capable of arriving at the conclusion that D. aridus really does cause dry lips. He might not even care if Koch’s postulates have been fulfilled. The true believers in the dry lip germ might even seem to have a religious conviction that people need to be vaccinated against dry lips or else be shunned from society so that they don’t “give” everybody else dry lips, a deeply religious conviction similar to that of Jennerism as described by Charles Creighton in the previous subsection. The people who are against vaccinations and mandates would look crazy to these people, or even evil. Of course, if the dry lip germ true believer lacks a scientific attitude, he will never explore both sides of the issue—he will be content to just believe whatever the “experts” on his television tell him. In fact, when one understands that science is really an anarchic process of debate, one understands that anyone who would attempt to shut down debate over the etiology of dry lips is really someone who doesn’t want science to happen. When it’s clear that the vaccinations against dry lips just aren’t working, instead of being curious about whether the treatment is based on a flawed understanding, the dry lip germ believer will double-down: “It’s not that the vaccine doesn’t work,” he thinks, “only that not enough people are getting vaccinated!” Decades or even centuries into the future, only after enough people look at these issues with an open mind (and possibly only after having already injected many millions of children with who-knows-what) would it come to light that the vaccines were ineffective against dry lips, and that the cure to the disease was to be found in a theoretical framework laid on an entirely different foundation. Oops! All the while, there probably would have been many more people afflicted with dry lips than there otherwise would have been, since their drugs wouldn’t have worked (or, at the very least, they wouldn’t have worked by the mechanism they claimed, and probably would have come with nasty side-effects since they were poisonous by design). Rather than having fewer people with dry lips, they ended up having more people suffering from dry lips, all because of their deep hatred for science and their preference for blind faith in fallible human “authorities.”

There’s a lesson to be found both in the historical cases of scurvy, beriberi, and pellagra, and also in our hypothetical world in which people believe that dry lips are caused by a dry lip germ: We always have to be extremely careful not to prematurely fool ourselves into imagining that a disease is caused by a germ, when in reality it’s not, especially if there isn’t any good evidence that it’s caused by a germ. It cannot just be said that correlation is causation—it must always be very rigorously shown that the suspect microbe is the cause of a disease, and not just a microbe that thrives in certain kinds of diseased tissue. In the exact same way that one person getting scurvy or dry lips after another person is not at all proof of contagion, one person getting sick after another is also not at all proof of contagion—not even in the slightest. If we aren’t especially rigorous in demonstrating that a germ is the cause of a disease, then we could end up putting our health and our lives at risk when we live by a false paradigm. Instead of fixing the root causes, we might even end up consuming poisons, killing innocent microbes in a vain attempt at obtaining health.

But with the ancient origins and strange early history of germ theory uncovered, with a major alternative (yet neglected) hypothesis made explicit, and with the importance of empiricism and Koch’s postulates understood, we can begin to study the more recent history of germ theory, from Pasteur to the present. How many times were nutritional and toxicological causes ruled out? How many times have Koch’s postulates been fulfilled, definitively proving that a disease is caused by a certain microbe?