When developing a medival fantasy realm, especially one with no known healing and restoration magic, one may need to develop the people's understanding of science and medicine. A unique example of this is in Patrick Rothufuss's "A Wise Man's fear", where someone from an altruistic organization called the Amyr performed human experiments for the purpose of collecting data that aided in saving many human lives in the future, despite the hundreds of tortured human lives that were sacrificed to produced such data.

My question is how can I develop a people's understanding of the germ theory as early as the middle ages, even if only the rich and educated get exposed to such knowledge?

  • $\begingroup$ Limited magic, or non-existent magic? Literature, or gaming? For fantasy RPG, I found it best to state, rather clearly in the opening, that "our" knowledge doesn't hold... if you accept magic, you can just as well toss germ theory, and the whole periodic table of elements while you're at it. Makes it much easier to "explain" what the healers / alchemists are doing. ;-) $\endgroup$ – DevSolar Oct 30 '18 at 15:33
  • $\begingroup$ Defining the magic i am using in the world i'm trying to build is rather difficult, since much of it is supposed to be lost and forgotten. but ill try to be more specific. $\endgroup$ – Austin Trigloff Oct 30 '18 at 20:44
  • $\begingroup$ @Austin then for the purposes of the question, say “no magic.” $\endgroup$ – SRM Oct 30 '18 at 21:05

The Middle Ages is normally said to be between the 5th and 15th centuries (so 400-1400 AD).

Germ Theory was first proposed in 1546 (!), close to the Middle Ages. It's not clear if Girolamo Fracastoro meant cells and bacteria as we know it today, but the core idea is there.

So you really have little to do beyond making influential figures of the period (e.g. A King or two) become convinced it's the right theory and back it. Perhaps another person or your character who proposes the idea is fortunate to have a powerful patron who lets them, e.g. try out improvements in basic hygiene and something as simple as masks and gloves when dealing with blood injuries or similar systematic approaches to dealing with illness. Perhaps the results impress the powerful patron and leads to wider publication and more widespread use. And in time to an early development of the theory and it's applications.

The compound microscope was invented sometime around 1590. Again just outside the Middle Ages. The combination of these two inventions in the right hands and with the right patron would be enough to get things going well. Probably this can be reasonably be made to happen a little earlier (say 1400). The microscope is important as it lets you see something to attach a theory to. "Have a look at this, Oh Wealthy Patron" works a lot better than "I have this wild idea, Oh Great One". It won't prove germ theory, but it will help advance the idea.

A King or Emperor who has a great interest and belief in sciences would be very useful. A King whose heir also has that interest would be better. Science needs money, lots and lots of money. :-)

As an aside you need to explore how science was done in the Middle Ages to get a feel for the way it would happen.

  • $\begingroup$ I think Roman glasswork might've been able to make microscopes... $\endgroup$ – Malady Oct 31 '18 at 3:05
  • $\begingroup$ @Malandy Very early lenses appear to have been of material other than common glass - quartz, for example. That's my very limited understanding. I'm not sure when manufactured glass started being used for optics, although I don't think this matters with reference to making a basic microscope. $\endgroup$ – StephenG Oct 31 '18 at 7:11
  • $\begingroup$ Well, lenses, yes, but reading stones could be made from glass. Make them thinner and set them in frames, to make glasses. ... In an alternate history, it wouldn't be impossible for Roman glassmakers to make microscopes with then-current techniques or with a little innovation? $\endgroup$ – Malady Oct 31 '18 at 14:28

We already had it and ignored it

There was a Greek general Thucydides from the 5th Century BC (no relation to our fellow resident answerer as I understand it) who first postulated the theory of contamination being spread by 'Seeds', or small objects invisible to the eye.

We ignored this in any serious scientific way, preferring the idea that deities and potentially their familiars (think cats during the Black Death) were responsible. It wasn't until Louis Pasteur that we really started to resurrect this idea as a serious scientific line of enquiry.

In many ways, this is similar to the Ionians who in the 13th century BC (or thereabouts) first articulated that the earth orbited the sun as part of a solar system before that idea disappearing for over 3 millennia.

The best possible way to enable the idea of germs during medieval times is to have taken Thucydides' observation and handed it to real Greek scientists to explore and develop as part of their research pursuits. If we didn't lose it in the first place, perhaps the dark ages wouldn't have been so... well, dark.

Just saying.

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    $\begingroup$ The Greeks came up with a lot of pet theories (they also postulated the existence of atoms, and "atom" itself comes from a Greek term), but they had absolutely no way of proving or disproving them. It's easy for us to say that this theory was correct in hindsight, but far harder for anyone in that time to have real evidence. $\endgroup$ – Cadence Oct 30 '18 at 6:28
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    $\begingroup$ @AustinTrigloff - Ignorant race in contrary to? $\endgroup$ – Battle Oct 30 '18 at 10:13
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    $\begingroup$ @Battle You mean in comparison to, as in contrary to is a topsy-turvy way of looking at it. $\endgroup$ – a4android Oct 30 '18 at 12:32
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    $\begingroup$ We already had it and ignored it multiple times, in fact. As late as the 18 (or 19th?) century there was at least one doctor proposing washing hands to prevent diseases. The guy observed measurably and pretty decidedly that when he instituted that policy in a hospital then deaths went drastically down. He was ignored and the reduced death toll was attributed to a new air conditioning system which better sucked out the "miasma" (bad air that caused sickness). Others have also suggested cleanliness through the ages when they observed similar things. $\endgroup$ – VLAZ Oct 30 '18 at 14:42
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    $\begingroup$ Essentially, until you get a scientific method and a reliable data storage, you have the “dark ages” periodically at various places around the world. You want germ theory faster? Then get scientific method and printing press established sooner. That’s what turned the corner. $\endgroup$ – SRM Oct 30 '18 at 21:09

In a rudimentary way, people already knew. More precisely, they observed that many illnesses would transfer to another person when they got in contact with an ill person, but they didn't understand why.

This led to very different ideas like

  • An illness is a punishment from God. Those who conspire with afflicted people deserve to be punished (infected) as well.

  • An illness is caused by bad smells (Malaria literally means "bad air"). This led to people avoiding the manure in their cities and using good-smelling herbs as medicine. They got the cause wrong, but the result was right in most cases.

  • People observed that most illnesses spread through close contact between ill and healthy people. In times of highly infectious epidemics they build quarantaines to seperate ill people from the general public.

  • They had a twisted understanding of cleanliness. It was thought that changing your underwear (a long garment like a night gown) at least once a day (twice a day for infants) was the definition of "clean". They neglected personal hygiene like washing their hands and faces with soap, which evidently lowers the risk of contagion.


As a very specific example, there's nothing about Louis Pasteur's swan neck flasks that preclude them from being demonstrated much earlier than the 1860s.

Possibly not enough on its own to get you all the way to a full germ theory, but it could be a pretty useful step along the way.


wouldn't have to necessarily develop a germ theory, so much as pragmatically adopt the hallmarks of infectious disease control, some of which were known in the late-roman/byzantine/arab world:

  • quarantine
  • frequent bathing, changing of dressings/clothing/bedding
  • clean clothing & bedding by boiling
  • clean fresh water supply
  • well-functioning sewage system

this could all be rolled into a hygienic aesthetic, perhaps a cult


Please refer to the novel "On the Oceans of Eternity" by SM Stirling for a very interesting take on that question. A group of Americans who were transported back to the 2nd millenium BC, try to teach the Sumerians how to protect themselves from germs. They have to integrate this into religious beliefs and daily rituals.

If I recall well, they use the Inanna and Enki myths to justify the hand washing rituals, boiling drinkable water, etc.


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