Answer: The adjective "medieval" (or sometimes "mediaeval" or "mediæval"), meaning pertaining to the Middle Ages, derives from medium aevum. Medieval writers divided history into periods such as the "Six Ages" or the "Four Empires", and considered their time to be the last before the end of the world.
Explanation:
Capitalism is my best guess, considering it is one of the few forms of economy that allows mostly free production. Free enterprise could also be the answer.