During the second half of the 12th century, the number of cases of heresy in Europe grew to worrying proportions. The Church consequently looked for effective ways of wiping out this phenomenon.

In France, the Inquisition arose from the terms of the Treaty of Paris, which was signed beneath the towers of Notre Dame on 12 April 1229. This agreement put an end to the second Albigensian Crusade and certified, in the presence of Saint Louis, King of France, the commitment of Raymond VII of Toulouse to banish the Cathars from his earldom.

On 13 April 1233, Pope Gregory IX officially established an inquisitorial system in France by announcing that he would be conferring unlimited authority upon the Preaching Friars to combat heresy and appointing F. Robert, known as le Bourge (or the Bourgeois), as General Inquisitor for the Kingdom.

These events marked the end of the principle expressed by Bernard de Clairvaux: Fides suadenda non imponenda (faith must be persuaded, not imposed), and although heresy may not date from the 13th century, the implementation of a legal procedure was a completely new concept in Europe.
 
 
The Inquisition was set up as a special tribunal whose jurisdiction was limited to defending the faith. In addition to its investigative activities, the Inquisition was invested with the dual function of employing harsh measures and punishing. It did not, however, act alone, as the civil authorities were in charge of armed repressions and executing the sentences.

It was created as part of the fight against the Cathars and Waldensians, and its activities spread to all fields in breach of the dogma or those encompassing witchcraft and philosophy. Even science was affected if it was considered to be adopting a non-Aristotelian outlook on the world. Galileo himself was obliged to abandon his theory on heliocentrism before the Tribunal of the Inquisition in 1633.

The Inquisition took hold throughout France. In the north of the Kingdom, the Inquisition appeared to act in a rather unmethodical and disorderly way, whereas inquisitors in their droves besieged the southern half, which was scene to some of the most major cases of heresy at the end of the Middle Ages. The Inquisition therefore had a fixed base in the Languedoc region with travelling tribunals comprising 5 or 6 inquisitors for the rest of the Kingdom.
 
   
(enlarge) The Pope and the Inquisitor, a painting by Jean-Paul Laurens, 1882, Bordeaux Musée des Beaux-Arts.

The inquisitor, Torquemada (1420 - 1498), with his index finger pointing down at the table, can be seen dictating his projects to Pope Sixte IV. This scene illustrates the secret advisory sessions held with the Pope.