:Well, Dr Luther's "strong and sturdy" belief in a "world that includes the Devil" (dualism is a different thing which, except in name, apparently did not enter your question) were shared by just about anybody at the time period, and is shared by all traditional (i.e., "orthodox" in the sense Chesterton uses the word in the book of the same name) Christians at this very moment, among whom I may include my unworthy person. What happened in the witch persecutions was, first, a downfall of reasonable trial (for the charge of having used witchcraft, e. g. a spell, was first of all just that, a charge); second, a mass hysteria; and then, third, perhaps also something about actually wrong beliefs concerning the witchcraft which I lack both the knowledge and the place here to go into detail.   (Catholic)