Whereas the barons of England forced King John to allow them a voice in important decisions, not every king in Western Europe needed coercion. For example, take Alfonso IX of León and Galicia (a very large percentage of the Iberian Peninsula).
Born 15 August 1171, he was 17 when he succeeded his father, Ferdinand II. Wars with Castile had left León in an economic downturn, and Alfonso's first need was to raise taxes, including on the lower classes. This led to revolts in several towns. That, and the continued threat from Castile, prompted Alfonso to summon León's nobles, higher level clergy, and merchants and tradesmen as representatives of several towns, to a Cortes at the Basilica of San Isidoro.
The Cortes ("court") of León of 1188 was the first formal uniting of the Three Estates (Nobles, Clergy, Commoners) in Western Europe. The Cortes laid out rules that are familiar to modern constitutions: the right to private property, to appeal to justice, to the sanctity of the home. The Cortes also demanded oversight of royal spending. As one modern scholar* put it:
Thus, the "plain state" was incorporated into the nascent Cortes of the Kingdom. In this way, the Roman proverb applied: "what concerns everyone must be approved by everyone." Thomas Aquinas clarified that "to guarantee the common good it is necessary that rulers be elected by the people from among the people."
The Cortes of León pre-dated the Parliament of England by decades. I was careful, in the second paragraph above, to specifically refer to "Western Europe," because of course there is at least one notable example of "rule by committee" if we look northward from the Mediterranean at the witenagemot.
Alfonso is also known for a different historical precedent than the Cortes of 1188: his reign mirrored some of Henry VIII's troubles with marriage(s) and the pope. Stay tuned.
*(Thank you, Google Translate)
