The Feast of Fools, dominated by the churches, had been the most important carnival festival in the medieval France. The earliest definite record on the Feast of Fools appeared in the second half of the 12th Century. Its rise or cause for concern in this period might be due to two main reasons: the anxiety of the millennium as well as the beginning of the campaign toward faith ''purification.'' It has been long, but wrongly, believed that the Feast of Fools was the festival for the lower clergies only. In fact, considerable evidence has proved that in the Middle-Ages, the feast encompassed supporters and participants from virtually all social strata, genders and ages, including senior clergy and the nobility. In other words, the upper classes did not reckon the vulgar carnival celebrations to be dishonorable or shameful, and they are themselves openly engaged in the same carnival games, too. This typically reflects the community-oriented lifestyle in the medieval France, in which all members shared the same cultures, beliefs and lifestyles. The fundamental reason for that is that the medieval people lived in a world full of a variety of real and imagined, natural and supernatural threats, and therefore needed to expel their fears by certain common religious rituals as well as to unite all community members to confront these difficulties. The Feast of Fools carnival games possess both of the above features, and thus were crucial for the people of the time. That explains why there was little progress for centuries despite the fact that someone had always been opposed to Feast. It was not until the 14-15th centuries that, when the traditional church and social systems were shaken by the Black Death, the Great Schism, the Hundred Years War and other profound social crisis, began the collapse of the traditional church and social system. New requirements were raised as to the proper conducts of the Church and the clerics. The new religious ideas, represented by nominalism, started the process of ''rational'' separation between religion and secular lives. In this context, the churches began to expel the Feast of Fools celebrations from its territories, followed by prohibiting clergies to participate in public plays. The Feast of Fools declined and gradually disappeared in the mid-16th Century. These developments also marked the disintegration of the traditional communities as well as the alienation and conflict between elite culture and popular culture. From then on, popular culture became synonymous to the like of vulgar or disorder, and turned in to the object of reform and repression. However, the Feast of Fools carnival still demonstrates profound positive influences on the modern culture of the West, such as expanding the cultural tension and diversity, and providing an ideological basis for the utopian theories and communal autonomy concepts.