Revolutionary Thought of Medieval Europe
"We must obey God rather than men" - says Saint Peter (Acts 5:29). "Let every person be subject to governing authorities. For there is no authority except from God, and those that exist have been instituted by God" - says Saint Paul (Rom. 13:1). These two instructions lead potentially to two extremely different views - revolutionary and counterrevolutionary. Until today, every politically conscious Christian must define his position somewhere between those extremes.
For the first time in European civilisation, christianity questioned the unity of religious and secular authority (unquestioned in, say, orthodox judaism or ancient Rome). By creating separate hierarchy of church and state, and separate codes of laws, it has achieved a theoretical possibility of complete separation of those two orders (even if not accomplished in practice).
The consequences were also revolutionary: if we assume the existence of law and authority that are supreme to the secular law and authority, we assume also a possibility of condemnation of the secular ruler in the name of God or divine law. Hence the question - what to do with an unjust ruler, e.g. with a tyrant - became one of the most interesting topics of medieval theology. The case of King John of England proved, that this was not only an academic discourse.
In XII century John of Salisbury maintained the most extreme revolutionary view. In his work "Policratius" he claimed, that killing a tyrant is not unlawful, because even if a killer violates secular law, he acts in accordance with God's will. King Henry II wanted to kill him for this treaty; John fleed to France where he became the bishop of Chartres.
Saint Thomas Aquinas (1225-74) considered this view dangerous, because it could encourage some individuals with perverted minds to kill their kings on their own judgement. Nevertheless, Aquinas also condemned tyranny and - after Aristotle - advocated moderate democracy as the best form of government. He saw the state as a form of social trust, and declared that "[its] proper object is the well-being of the whole community". In Aquinas view, the supreme authority belonged to the people. "For this reason if rulers (...) command things to be done which are unjust, their subjects are not obliged to obey them. As Aristotle, Aquinas considered the violent change of government an evil that should be avoided, but being necessary and legitimate in some cases.
Medievals thinkers, just as the ancient ones, did not use the word "revolution" - they called it "tyrannicide", a tyrant's slain. But soon northern Italy becames divided into many independent city-states, just like ancient Greece. In 1355 a popular uprising overthrows oligarchic rule in Siena, and the word "rivoluzione" is used for the first known time in history.