Like uAFGNCAAPParadigm said , the witchcraft argument was basically only used for negative effects no one could explain , and almost all people accused of witchcraft were outsiders of some sort , like minorities or antisocial people who lived outside the villages , etc . If you accused your neighbor of witchcraft and he had a good reputation in the community , which a doctor would certainly have , character testimonies from friends and peers and maybe even influential people in the village ' s community would almost certainly lead to the charges being dropped . Contrary to popular believe , pointing a finger and shouting That dude is a witch ! in the middle of the market place would not lead to them being burned at the stake immediately . This has also to do with the fact that the courts back then weren ' t populated by professional lawyers and judges like today , it were mostly just people from the community , often priests and officials . If you had a good standing with them , your chances of not being convicted were much better . In some of the bigger cases , the local capital or diocese would send over a representative to act as a judge and they were usually better educated and professional . Also , keep in mind that people were very much convinced that witches wanted them harm , because witchcraft was by its very definition a power granted through a deal with the devil and its users were always demonworshippers . So if you used your superpowers for good and in the name of God , you weren ' t a witch but rather someone who worked for the powers that be , and a doctor would certainly fall under this category . This white magic was very much a thing , based in Christian belief and focused on nature and medicine . There was such a thing as goodluck spells , health spells , etc . Not all alchemy was evil per se , even though it was a slippery slope . If one of your potions backfired because you used a herb that was kind of poisonous and had a negative effect , you could easily be pushed into the black magic pot , but if we assume that our time traveler knows his shtick this wouldn ' t happen . A witch by medieval definition was not just a spellcaster like what we see in Harry Potter but an evil person who wanted to harm the community . So if someone accused you of using witchcraft to cure people , it would probably rather fall back on them because you were the one doing good and they tried to stop it . On top of that , science was also a thing even back then . It of course wasn ' t as sophisticated or wellunderstood as it is today , but if someone came along and said , cholera is caused by unclean water and contaminated food , people would have been able to understand that reasoning and if they saw results , they would probably believe it as well . TLDR cholera appears and no one can explain why fucking witches did it cholera disappears and no one can explain why praise the Lord .