Nichola wrote:
Actually, in a pre-modern society, infectious disease is a huge problem, much bigger than war and likely larger than starvation. Penicillin, once introduced with a feasible production method, would almost certainly persist, if only available to the wealthy.
The usefulness of Penicillin vs the cost would probably make it worth making a extra money for. Even the poor could afford it if given a reasonable chance. Even the rich taxing the poor would find they got more money from living taxpayers then it cost them to provide Penicillin when necessary. It can be grown in vats of water and corn syrup - not a complicated or expensive process.
Crop rotation and higher yield crops, animal husbandry, medicine would increase the production of food, nutrition, survival etc. With higher production the poor get less poor, the rich get to tax more and get more rich. It is what has powered the modern era but it could be introduced effectively much earlier.
Something as simple as the Black Plague: "stop killing the cats! Kill the rats you idiots!", don't live in your own sewage, drink clean water, get more protein. Government cheese and grainaries, elementary education.
There are lots of low cost high value changes that can be introduced.
I'm pretty sure basic refrigeration would be easy to do with air as refrigerant, a bellows pump and lead piping run off a windmill or water wheel. Add copper wire and a load stone and you've got a generator instead. You don't need a refrigerator in every house - even a single cool room in the castle would be useful.
There are lots of low cost high value changes that can be introduced.
But I feel to have a major effect these ideas have to be introduced in a society with written language and existing in at least a basic farm economy. Bringing "magic" to a prehistoric tribe is posiably useful to the tribe but oral history is not a good means of conveying knowledge from generation to generation and if it never spreads past the tribe then it's good is extremely limited.
Dependable advances in science and knowledge come with written language and ideas shared across times and distances - one idea building on another.
If you want to have an idea work you just need to show the rich how they benefit from it. If well fed, healthy, educated peasants means the king gets richer then it shall be (and make sure the church gets their cut also).