IIN THE LATE NINTH CENTURY medieval intellectuals described Christian society as composed of those who pray (the monks), those who fight (the nobles), and those who work (the peasants). This three-category model does not fully describe medieval society — there were degrees of wealth and status within each group. Also, the model does not take townspeople and the emerging commercial classes into consideration, and it completely excludes those who were not Christian, such as Jews, Muslims, and pagans. Furthermore, those who used the model, generally bishops and other church officials, ignored the fact that each of these groups was made up of both women and men. Despite — or perhaps because of — these limitations, the model of the three categories was a powerful mental construct. Therefore, we can use it to organize our investigation of life in the Middle Ages, broadening it to include groups and issues that medieval authors did not. (See “Monastic Life” for a discussion of the life of monks and nuns — “those who pray.”)