One of the reasons that the Salem Witch Trials have attracted so much interest from scholars and the general public is that there remains no consensus as to what actually caused them. Historians have argued that their origins lay in deep seated misogyny, anxiety over political changes and Indian wars, petty land disputes within Salem, food poisoning, and a host of other factors. They have been compared to other examples of mass hysteria in which individuals were denounced on flimsy evidence, most conspicuously the McCarthy trials and the actions of the House Un-American Activities Committee.
The lesson is not so much what types of events can spark terror and hysteria, but rather that people tend to respond to these feelings by scapegoating and denouncing other people. Another lesson is that under such circumstances, people not directly involved in the accusations, as well as those in positions of power are sometimes willing to believe wild accusations that they might have otherwise dismissed. Whether it was spectral evidence in the case of the witch trials or unfounded rumors in the case of the HUAC or the McCarthy hearings, people were condemned, sometimes literally, sometimes in public opinion, based on the flimsiest of premises.