On many 'health' sites defending terrain theory (the theory that the state of the body, not just germs, is the primal factor for disease development) one finds quotes that Louis Pasteur is said to have admitted that terrain theory was right. Here, for example, Prestige Wellness Center from Dr. Ray Andrew:

By contrast, Pasteur’s friend, physiologist Claude Bernard, taught that the ‘terrain’ of the human body was more important than the ‘pathogens’ that infect it. We are surrounded by, and even harbor, microorganisms in our bodies. When exposed to pathogens, we become ill if our defenses are weakened by deficiencies or toxicities. Unlike the germ theory, the terrain theory explains why some people get sick while others, when exposed to the same pathogens, do not. For this reason, it is said that on his death bed, Pasteur admitted, “Bernard was right: the pathogen is nothing, the terrain is everything.”

In English medical literature this quote is traceable to at least Hans Seyle and his book The Stress of Life from 1956:

Yet Pasteur's work on immunity induced with serums and vaccines shows that he recognized the importance of the soil. In any event, it is rather significant that Pasteur attached so much importance to this point that on his deathbed he said to Professor A. Renon who looked after him: "Bernard avait raison. Le germe n'est rien, c'est le terrain qui est tout!' ("Bernard was right. The microbe is nothing, the soil is everything.")

But before that occurrences get rather thin and Seyle doesn't provide a source for this.

Did this really happen?

  • 12
    These sort of claims (a similar, and more common, version is that Darwin renounced evolution on his deathbed) imply a worldview in which scientific theories depend not on the evidence for them, but the authority of their original proponents. The claims are nonsensical unless the implication is that the proponents have some secret information that invalidates their theories that they were hiding all those years. Otherwise, it's just the opinion of one person that has no bearing on what the evidence is. May 10 at 19:23

1 Answer 1


This can be traced to a questionable 1922 anecdote.

Okay, I have an answer now.

The original French quotation, "le terrain est tout, le microbe n’est rien," was in vogue among doctors in the 19th century, as seen for example in a review of the 1885 book Leçons de clinique médicale by S. Jaccoud:

he becomes an eclectic sage, as we used to say, and insists perhaps too forcefully on the importance of the terrain: the terrain is everything, the microbe is nothing. ("il devient d'un sage éclectisme, comme on disait autrefois, et insiste avec trop de force peut être sur l'importance du terrain: le terrain est tout, le microbe n'est rien.")

Lyon médical, Volume 48, 1885

or in this 1902 German review:

Opposition to the doctrine that infection with the tubercle bacillus alone is sufficient to cause tuberculosis or even phthisis has visibly gained ground in recent years. Everyone, especially the practitioners, is working hard to prove that hereditary disposition is the actual beginning of the disease -- "que le terrain est tout, et que le microbe n'est rien". ("Die Opposition gegen die Lehre, dass die Infektion mit dem Tuberkelbacillus allein ausreiche, um Tuberkulose oder gar Phthise zu erzeugen, hat in den letzten Jahren sichtlich an Terrain gewonnen. Von allen Seiten, namentlich von den Praktikern, wird eifrig daran gearbeitet, den Nachweis zu führen, dass die hereditäre Disposition der eigentliche Beginn der Erkrankung ist, „que le terrain est tout, et que le microbe n'est rien".")

Aronsohn, Ed. "Beziehungen zwischen Tuberkulose und Krebs." DMW-Deutsche Medizinische Wochenschrift 28.47 (1902): 842–845.

By 1962 this phrase had become associated with the antivaxxer movement.

Vaccination is a method constantly denounced. It is, alongside [the loss of natural] bread, the other “major plot”... The general conception of health presented ... defends the idea of “natural immunization by purification of the internal environment: the microbe is nothing, the terrain is everything” (LVC, n° 172, March 1962). ("La vaccination est une méthode constamment dénoncée. C’est même, avec le pain, l’autre « complot majeur » ... La conception générale de la santé présentée ... défend l’idée « d’une immunisation naturelle par purification du milieu intérieur : le microbe n’est rien, le terrain est tout » (LVC, n° 172, mars 1962).")

César, Christine. « Les métamorphoses des idéologues de l'agriculture biologique. La voix de La Vie Claire (1946-1981) », Écologie & politique, vol. 27, no. 1, 2003, pp. 193-206.

So, who first attributed it to Pasteur? This information cannot be found on Google Books/Google Scholar but it is in BnF Gallica.

Another legend to be destroyed: Pasteur, affirm those ignorant of his work, saw diseases as the work of germs alone, and ignored the importance of the terrain that causes germs to develop. A famous novelist of the end of the 19th century, a great friend of Dieulafoy, even went so far as to claim that Pasteur, shortly before his death, confided to one of his close friends: “I was wrong, the microbe is nothing, the ground is everything”. Pure invention of the novelist! ("Une autre légende à détruire : Pasteur, affirment les ignorants de son œuvre, n'eut en vue dans les maladies que le germe infectieux, il ignora i’importance du terrain pour le développement du germe. Un romancier célèbre de la fin du xix^e siècle, grand ami de Dieulafoy, alla même jusqu'à prétendre que Pasteur, peu de temps avant sa mort, aurait confié à un de ses intimes : « le me suis trompé, le microbe n'est rien, le terrain est tout ». Pure invention de romancier!")

Bulletin de l'Académie nationale de médecine, 21 Nov 1946

Basically, this quotation says that the attribution to Pasteur arose at around the same time period that the phrase was in vogue. I think it is plausible that the original use of the phrase was a lazy shorthand describing French doctors who sought out what we might call preventative medicine, and was then exploited by a "novelist" falsely caricaturing Pasteur as a germ-crazy fool unaware of bodily conditions. Some decades later, this sort of caricature evolved into an entire pseudoscientific "terrain theory" although doctors never denied the importance of "terrain" in the first place.

The "novelist" in question is Paul Bourget. From Google Books, it looks like he initially published this anecdote in a 1922 issue of L'Illustration:

Professor Renon, who has just died prematurely, told me that, watching Pasteur during his last illness, the latter, whom he thought was asleep, had woken up from an indefinite reflection to tell him: "Renon, it is Bernard who was right. The germ is nothing. The terrain is everything." ("Le professeur Renon, qui vient de mourir prématurément, me racontait que, veillant Pasteur durant sa dernière maladie, celui-ci, qu'il croyait endormi, s'était réveillé d'une réflexion indéfinie pour lui dire : « Renon, c'est Bernard qui avait raison. Le germe n'est rien. Le terrain est tout. »")

This also appears word-for-word in his 1929 book Au service de l'ordre, on p.199. L. Renon was a real doctor at l'Hôpital Necker. However, according to an affidavit drawn up at the time of Pasteur's death, the attending doctors were named Emile Roux and Louis Vaillard.

  • The claim contains a quote: Pasteur just repeats Bernard (or Béchamp in some versions, there are a few: word choice, word order, 'near end of life' vs 'last words' 'death bed' etc). So the quote is definitely older than 1950s, & en vogue in 19cent, indeed from the original debate between Pasteur and his opponents. Whether LP indeed 'recanted' (or not/in some form) cannot be proven by this, and the (radicalised) context is important: the value of the terrain is ecological, germs not absolute rulers. If LP approached such synthesis, that's very different from 'germs are nothing' denialism. May 10 at 11:01
  • To complement: Early biographer René Vallery-Radot (his son-in-law) seems to document one version of 'last words': 'no such thing as the claim'. But his biases give a slight taint and LP's death was somewhat prolonged. These biases around LP make this hard to decide for reliability: his 'defenders' are all to quick to deny this, his modern opponents all too quick to accept teh quote as 'proof'/'genuine'. May 10 at 11:09
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    I'm in agreement with you on the medical part, I just think the quotation is so pithy that it's meaningless except as caricature or propaganda. Hence the false deathbed attribution
    – Avery
    May 10 at 11:09
  • 1
    What is the answer? I can't get if the claim is true or not from this
    – Joe W
    May 10 at 12:12
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    I believe the claim is false but I have no clear proof, this post is mainly to trace it to a specific author and give context for the claim
    – Avery
    May 10 at 13:27

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