The Inquisition was a office of the Catholic Church charged with suppressing heresy. There have been four different Inquisitions; their actions and interactions with the local governments are subjects of considerable historical enquiry.
One common misconception is that the Church executed heretics. While this did happen, in most jurisdictions and at most times only the secular power had the authority to perform executions. The Church would declare the person a heretic, and call on the secular power to perform the execution.
The first, known as the Medieval Inquisition, was established in 1184 in response to the Catharist heresy in southern France and faded in power with the successful suppression of that group.
The infamous Spanish Inquisition was not an ecclesiastical operation at all. It was established in 1481 by Ferdinand and Isabella to investigate and punish the Jews and Moors who had publicly converted to Christianity but had privately continued to practice their prior religion and were thus, by definition, heretics. Prior to their expulsion from the country in 1492, Jews or Muslims who did not become Christians were not subjected to the powers of the Inquisition.
Less known is the Portuguese Inquisition, which rivaled the Spanish in its infamy.
The Roman Inquisition, begun in 1542, was quite distinct from either of these. It was the least active and most benign of the three variations.
further reading:
- Edward M. Peters, Inquisition. (University of California Press, 1989). ISBN 0520066308
- ---A brief, balanced inquiry, with an especially good section on the 'Myth of the Inquisition'. This is particularly valuable because much of the history available in English of the Inquisition was written in the 19th century by Protestants interested in documenting the dangers of Catholicism or Catholic apologists demonstrating that the Inquisition had been an entirely reasonable judicial body without flaws.
- Henry Kamen, The Spanish Inquisition: A Historical Revision. (Yale University Press, 1999). ISBN 0300078803
- ---This revised edition of his 1965 original contributes to the understanding of the Spanish Inquisition in its local context.