The Inquisition is another thing, besides the Crusades, that some people hold against Christianity. For this reason, I would like to learn more about it. Here is a brief summary from what I have studied so far:
“One of the strengths of the medieval papacy in maintaining its power over the populace of Western Europe was the Inquisition. In the process of development for a couple of centuries, the medieval Inquisition came to its definitive formulation under Pope Gregory IX (1227-1241). The reason for its implementation at that time was the decision of the Holy Roman Emperor Frederick II in 1232 to issue an edict assigning the apprehension of heretics to state officials.
Gregory feared that Frederick would use this effort for political ends and also did not want to surrender the management of church affairs to the state. As a matter of fact, the Fourth Lateran Council of 1215 had spelled out aspects of the Inquisition and the church was about ready to proceed on its own anyway.
The Inquisition was designed to inquire into the spread of heresy and to call before its Tribunals Roman Catholics suspected of heresy in order to secure their repentance. The program was launched merely to keep the faithful in line, not to obtain the conversion of Jews and Muslims. The great purges against those peoples in Spain were inventions of the Spanish throne after 1479. The Inquisition was deemed a necessity because of the spread of groups such as the Waldenses and the Cathari or Albigensians, which, if allowed to go unchecked, threatened the very life of the papacy.
Generally, the Dominicans or Franciscans were in charge of Inquisitorial activities. Trials were held in secret. There was no way of obtaining meaningful legal defense, because any lawyer representing an accused person would himself become the target of church tribunals. Confessions might be extracted by torture, and testimony against the accused might be obtained from witnesses by the same means.
Those who confessed and were reconciled were subjected to various punishments, including penances, pilgrimages, scourgings, or fines. Those who refused to recant commonly had their property confiscated, were imprisoned, or handed over to the secular authorities to be executed, usually by burning. The excesses of the Inquisition (sometimes called “an engine of iniquity’), its violation of human rights, and in some places its reign of terror, must forever remain as a blot on the history of the Roman church.”
(pp. 68-70, “Exploring Church History,” by Howard F. Vos)