How we change what others think, feel, believe and do
Inquisition, although based in the gentle term of 'inquiry' has historically been associated with more extreme query, as described here. Historically, inquisitions are associated with religion (and in particularly the Catholic Church), although they have also been widely used in varying forms by dictators and political parties.
The primary purpose of inquisition is to enforce a religious or ideological dogma by prosecuting and punishing heretics. The purpose is seldom about discovering truth or making legal prosecution.
This purpose is often achieved through confession and promise of returning to the faith -- an act that may be the best alternative for the accused (the alternative being imprisonment or worse).
Inquisitions may also be used to extract information from heretics -- typically about other heretics.
Religious inquisitions were generally held in secret, perhaps because the accused's friends might try a rescue, but more likely because, as a religious trial, it was outside the law and could be shut down by the legislature.
The accused person was generally assumed to be guilty unless proven innocent, and could be brought to trial on a single accusation. Accusation was often of a crime that could not be disproven, such as witchcraft.
Witnesses were often unknown and their names kept secret from the accused person. When the person was suspected of witchcraft, for example, it was intended to keep them from casting spells on the witnesses.
Questioning was far from fair inquiry, and the accused was generally assumed to be a liar, thus being trapped in the double bind of assumptions of lies if they pleaded innocence. Questions would also be loaded, such as 'Why did you not stop your guilty activities when you knew in your heart they were so evil?'
In fact pleading guilty by accusing others (particularly the bigger fish that the inquisition was seeking) of subversion was often the best ploy.
The accused often was not able to argue a case for the defense and may well be prevented by calling witnesses.
Extraction of a confession was allowed by pretty much any means, including deception, torture and other extreme methods.
Inquisitions, whilst very seldom of the old religious kind, are alive and well. Interrogation can easily become inquisition when the person is assumed guilty and extreme means are used to extract a confession. Truth thus becomes what is defined by the accuser and confession, even false confession under duress, is assumed as evidence of guilt.
Political inquisitions also still abound, even in relatively 'civil' countries, where show trials of former leaders and their followers are used to demonstrate the permanence of change to a new government.
Inquisitions can be relatively friendly, and the South African use of 'truth and reconciliation' helped them towards unity after many years of apartheid.