See also the chronophone (and its followup).
It seems like the Givewell branch of EA is the application of recent improvements in scientific management / finance to charity, about ~10 years after they appeared in the private sector, similar to CharityNavigator before it. If you can count those as "principles," then they might be a huge leg up for someone like the Fuggers. (Remember, double-entry bookkeeping in Europe seems to have started about 1340, and the first textbook on it was published in 1494.)
But if the chronophone would transmit that as just "apply recent advances in business to all your endeavors," that's not very useful, and maybe even not that--trade and business is the dominant force in the society that Givewell lives in. What would the dominant force in the 1400s be? Innovation is respected in the society that Givewell lives in. Would it be respected in the 1400s?
The chronophone is a weird device with weird limitations suited to the purposes of EY in that post.
This is a much more straightforward question (but note the context -- it asks where should that person put his money, not what kind of tech he should invent).
In particular, there is an interesting implication/sub-question: what was the cheapest way of saving the most lives in 1400 and do you think that was the best use of resources?
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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