An inquisitor was an official (usually with judicial or investigative functions) in an inquisition – an organization or program intended to eliminate heresy and other things contrary to the doctrine or teachings of the Catholic faith. Literally, an inquisitor is one who "searches out" or "inquires" (Latin inquirere < quaerere, 'to seek'). Inquisitors sought out the social networks that people used to spread heresy. There were accounts where the Inquisition could not tell who was a heretic or devout, and they were killed anyway. One of these accounts was Arnaud Amalric at the storming of Béziers. The abbot was recorded as saying “Kill them. For God knows who are his.” This brought up concern about the role the Inquisition was playing and whether or not it was a truly righteous cause.
The role of the Inquisitor was further brought into question by a work of satire by author Dostoyevsky. In this prose poem, Christ came back to earth and was imprisoned by the Grand Inquisitor. The Grand Inquisitor argued that Christ couldn't be free because his work would directly oppose the church, because free will was a burden to humanity. Dostoyevsky ends the poem by saying that the Roman Empire secretly followed the work of Satan instead of Christ, due to Satan allowing the best form of order for Humankind.  In this story, the Roman Empire used Religion as a way to control the average population. This made the Inquisition out to be a war on ideology and free will, as opposed to a suppression of heresy.
Some of the better-known inquisitors throughout history include: