Monks and nuns are by no means just a phenomenon of the Middle Ages. Originating from hermits and monasteries in the Egyptian and Syrian deserts in the 3rd and 4th centuries, this movement quickly spread to Western Europe. It aimed for a consistently Christian life, but also sought to positively shape the world rather than deny it. Additionally, it aimed to make a statement against the rich and powerful. Despite these ideals, fanaticism and self-interest also emerged. By the time of the Council of Chalcedon (451), monasticism had already become a solid societal entity. Its influence on politics was significant, and the search for the true Christian faith did not always proceed peacefully. Rioting and violent monks became a problem for internal security in the Eastern Roman Empire. This provided sufficient reason for church assemblies, foremost the Council of Chalcedon, to address these issues. The book first shows how this development came about and further describes how these problems were resolved through council decisions, monastic rules, particularly the Rule of Benedict, and state laws. Monasticism, now integrated into the church organization, became a defining force in Europe and beyond, ultimately becoming one of the guardians of the ancient heritage.