What use was getting a confession out of someone in private, why put someone out of view in a penitentiary that no-one ever wants to go to and let their punishment be prolonged and purposeless? It’s just plain costly to keep them incarcerated.
No…the people of the middle ages were nothing if not economists. They went for full value punishments. Making people publically and fully confess their (supposed) crime or recant their position in front of all their community was an important and valued public statement to reinforce social mores. It said ‘I did it, and I was wrong. I called into question the whole sacredness of the order of society. Mea culpa.’
The heretic that went to their death reaffirming their heresy was a disaster because it called into question the entire basis of society. They might as well have said ‘You are wrong. I die knowing that you are wrong. And now you risk questioning it, too.’
As a result, normal people (and their young children) regularly attended public executions to publically demonstrate their agreement that the general rules of society were important and valid, and to privately reaffirm it for themselves. They were a vivid, effective and damage-limited reminder of why social rules were to be followed. But they also provided an opportunity for each person to privately reaffirm their beliefs/behaviours and discourage their own deviant elements.
There but for the grace of God…
Taken from The Great Courses’ Explaining Social Deviance Lecture 2: Demonism