Redderationem"Redde rationem". Order, calculation and reason in the urban societies of late medieval Italy. The final centuries of the Middle Ages were characterised by phenomena of exceptional magnitude: famine, epidemics, large-scale and prolonged wars, the creation of more efficient states, the development of Humanism, a new religious sensibility, the clash with the Ottoman empire, the opening of the great oceanic routes and much more. Late medieval Europe has long been represented as the bearer of the most extreme feelings both in a positive sense, hence the civilization of luxury and beauty, and in a negative sense, with its religious obsessions and social conflicts. At the same time, historians have discussed the concept of ‘crisis’ applied to the 14th and 15th centuries: at times they have supported the idea of a world that lost its brightness and faded towards increasingly grey and gloomy tones, other times they have embraced the thesis of a rebirth which followed a ‘creative destruction’ capable of breaking down the bonds of a feudal society in order to steer it towards modernity: in other words, the late Middle Ages must be looked at as Early Modern. This project embraces the second approach, in the belief that there is a common thread capable of uniting the worlds of late medieval Europe: rather than with the sphere of emotion, it had to do with a generalised need for order and rationalisation. This process, of course, was carried out according to categories and systems of rationality that do not necessarily correspond to contemporary ones: that is precisely why it is necessary to pursue a process of historical understanding in order to fully grasp the meaning of an era. The key term, which bridges various and otherwise heterogeneous areas, is ‘reason’. In the Italian vernacular of the time, “ragione” incorporates multiple meanings. In the first place, it recalls the good keeping of accounts. Moreover, ‘reason’ embodies the meanings of: reasoning, understanding, common sense, order and nature, motivation, strategy. ‘Reason’ in its meaning of calculation and right order is also the concept at the foundation of the growth of the public administrative apparatus, since it embodies also the verification of the correctness of public accounts. On the other hand, the term ‘reason’, an obligatory translation of the Latin “ius”, also becomes a synonym for administration of justice and law. The cities of Italy in particular, and of the nearby Christian Mediterranean, will be the focus of this project. The research will be developed around the following thematic areas: I. “Ragione” as the orderly keeping of accounts: ordering the accounting of private companies, and of public, ecclesiastical and charitable institutions. II. “Ordo” and “ratio” in legal and professional culture and practice. III. “Rationabiliter vivere”: ordering behaviours, sins and virtues from a religious and moral perspective.