Yes! Printing, much like the internet, allowed for the wide dissemination of information at a pace and scale which had been impossible previously. Like today, not all of that information was, strictly speaking, 100% factual. My own studies have focused mostly on the Protestant Reformation, where all sides tried to use the power of the printed word (and printed image) to its fullest potential. In the case of the Reformation I would probably use the term “propaganda,” rather than “conspiracy theories” or “misinformation,” but there is an awful lot of gray area between those terms.
Printing was developed in the 1450s. It takes time to build a printing press, of course, and more time still for printer’s apprentices to learn their craft. But in the following decades the technology spread quickly (by the standards of the 15th century), and by the year 1500 most major cities in Western Europe had at least one printer’s shop. The Reformation is traditionally said to have begun on October 31, 1517 when Martin Luther sent a copy of his 95 Theses to his archbishop. Within weeks the Theses had been published and printed in numerous cities around Germany; here is a copy printed in Nuremberg (200 miles from Luther’s home in Wittenberg) in late 1517. Now, I don’t think it’s fair to call the 95 Theses themselves conspiracy theories, propaganda, or even necessarily misinformation. But the speed at which they were printed and disseminated really showcases the capabilities of printing, and foreshadows the future course of the Reformation.
This isn’t the place for a general history of the Protestant Reformation. Suffice to say the Western Church split apart, and no one really held back when it came to what they were willing to say about each other (the “Lutheran Insulter” is a personal favorite of mine). There’s a difference between simple insults, like this 1545 woodcut of people farting on the pope, and explicitly calling the pope the Antichrist, like the images and texts from 1521 here. Images like this one from c. 1530 of the devil playing a monk like bagpipes alleged that the Catholic Church had been thoroughly infiltrated by Satan. As for flat out misinformation, look no further than rumors about the Renaissance-era popes. There are so many stories that it’s difficult to keep up with them all; Paul II allegedly died having sex with a page boy, Alexander VI’s son supposedly threw a massive orgy in the apostolic palace attended by 50 prostitutes and many high church officials (this rumor is based on a diary entry of the pope’s Master of Ceremonies, which was later greatly elaborated and widely printed), and so on. These rumors against the popes weren’t limited to Protestant sources, and they began before the Reformation; Stefano Infessura, an Italian historian of the late 15th century who was employed by a powerful Italian family, claimed that Sixtus IV was a “lover of boys and sodomites,” and that Innocent VIII, while on his deathbed, was fed the blood of three young boys who later died. These rumors were used by Infessura’s patrons against their rivals, but they found new life in Protestant works decades and centuries later. It’s hard to know if there is any truth to any of these stories, but modern historians have dismissed the most lurid rumors as exaggerations or outright fabrications.
Insults, rumors, and misinformation weren’t only being printed about Catholics, of course. This is a woodcut from 1529 portraying Martin Luther as a monster with seven heads (echoing the seven-headed beast of Revelation). One of the heads bears the name “Barabbas,” the bandit released by Pilate on Good Friday, clearing the way for Jesus’ crucifixion. This image from 1521 shows Luther working over a huge bubbling pot with the assistance of three demons and a raven; “blasphemy,” “heresy,” and “falsehood” rise up from the brew. The clear implication is that Luther is in league with the devil. For a later example of misinformation, see this (Latin, sorry) scan of a 1606 book called “Præscrptiones Adversus Hæreses”. It includes a false claim that Luther died by hanging himself after a night of heavy drinking.
A funny image today (or a lurid conspiracy theory) can go viral, spreading from person to person and website to website until it cannot possibly be controlled by any central authority. Documents in early modern Europe could spread in a similar way. It takes more time to set type or make a woodcut and then print a thousand copies of a pamphlet than it does to click “share,” of course, but in an age before nation-states and modern communication the authorities couldn’t respond very quickly either. Short documents, printed as placards (a single sheet) or pamphlets (a few pages) were quick to produce, quick to read, and (relatively) cheap to buy. It was these documents, printed by the hundreds and the thousands, that really fueled the cultural shift that was the Reformation. In essence, the Reformation represented a monumental change in the sources people looked to for knowledge. No longer was the Catholic Church the sole source of information. Anyone, not just the priest in the pulpit, could make their views known. Perhaps I’m toeing too closely to the line of the 20 year rule here, but a great deal of ink has been spilled in recent years comparing this breakdown in trust of the Church via the printing in the 16th Century to the breakdown in trust of traditional journalism via social media in the 21st Century; this article is one example. We shouldn’t equate things too closely, of course; the 16th Century was still an age before near-universal literacy, so even the most widely printed documents would only ever be read by the educated class. And in a time before elections and universal suffrage the opinions of the common people had less immediate influence on politics than they do in today’s liberal democracies. But there are useful comparisons to be made. And why study history at all if we can’t learn anything useful from it?
I mean, aside from having a laugh at a picture of people farting on the pope, of course. That’s always worth studying.
I think this is a very interesting question, but there's one interesting shift I want to suggest to the question before my answer. In 1500-1600, there was nothing established close to science. So it's hard to have a concept of "misinformation" or "conspiracy theories" in a similar way as we have it today. Bacon was just starting to re-popularize the idea of empiricism at this time, and it would take several hundred years for there to develop a concept of information which would resemble today.
For example, take this link https://royalsocietypublishing.org/toc/rstl/1780/70 of Philosophical Transactions (possibly the first scientific journal) from 1780. Mixed in with what we consider "science" would be things that would fit in with pseudoscience or conspiracy theories today. Right beside entries on mathematical equations, you have articles like " Account of an extraordinary appearance in a mist.". Other issues had reports of sea monsters and other concepts which would be right in line with current conspiracy theories. So the main point there is that there was any distinction between what we would consider misinformation versus information today when the printing press was invented.
However, if we shift the terms from establishment to anti-establishment, we see the pattern in the main question. The invention of the printing press allowed anti-establishment ideas to spread considerably. This is most notable for the use of the printing press in the Reformation, which really could be termed as many "reformations". Some of those reformations became more orthodox Protestant sects while many others were seen as quite unorthodox by any authorities. This would be the thing in the middle ages most analogous to a "conspiracy theory" today.
Similarities:
Religious sects with radical ideas could spread their information very quickly over long distances which would allow them to have a much larger reach. Some early printers embraced this because particularly inflammatory tracts would sell much better than ones that were quite orthodox, so this created even more motivation to spread these ideas (Eisenstein, 1980). Because printers were literate and were exposed to many ideas, some of these printers were religiously motivated and were converted by the ideas they read and became even more motivated to spread their unorthodox ideas. Others were much more profit motivated, but even then they were able to spread unorthodox ideas (note this only happened in some parts of Central Europe where the government allowed this).
Differences:
There was one major difference between the printing press and the Internet in spreading antiestablishment information: literacy. The printing press was invented in a time with very low literacy except among the educated elites. There were few books so literacy was not as important. The printing press drove a demand for literacy but this meant in the first generation the printing press was only influential among two very educated groups: clergy and educated elites.
This meant two important nuances: The main ideas spread more slowly. For example, Rubin (2014) showed that this spread of information from the printing press may have taken between 30 years to one century. Once the printing press increased literacy, the demand increased more quickly, but it still would have taken much longer.
Second, the effects of the early printing press were filtered to the general public through leaders who could read. In the Reformation, this was from religious leaders, either disgruntled clergy or other dynamic readers who would read the ideas and then spread them through preaching. This had the effect of filtering what was said and shaping many of the ideas in ways that were different than what was public. (it might be an interesting historical thesis to consider whether this is analogous to how information is shaped today by social media).
The final point I want to make is that in retrospect, we consider many of these anti-establishment ideas to be much more positive than the stereotype of misinformation today. The printing press is strongly associated with positive economic activity as cities which had presses would grow their economies much more quickly than those who did not (Dittmar, 2014)
Sources:
Jeremiah E. Dittmar, Information Technology and Economic Change: The Impact of The Printing Press , The Quarterly Journal of Economics, Volume 126, Issue 3, August 2011, Pages 1133–1172, https://doi.org/10.1093/qje/qjr035
Eisenstein, E. L. (1980). The printing press as an agent of change (Vol. 1). Cambridge University Press.
Rubin, J. (2014). Printing and Protestants: an empirical test of the role of printing in the Reformation. Review of Economics and Statistics, 96(2), 270-286.
