The treatise of Claude de Seyssel (1450—1520) should be discussed in the context of the Italian wars (1494—1559). His works, and especially “La grant monarchie de France” might have played a role of ideological works written in favor of the idea of “open diplomacy”. Claude de Seyssel pitted France against Venice as two different types of political systems, one open to all estates and another closed and putting in power only people of significant aristocratic status. Venice did have positive aspects of rule in his description, but it missed the system of counterbalances that the French monarchy did possess. The was an invective against the “covert diplomacy” that of Venice, which had been know to early modern Europe and which was the main problem of the new emerging unions between monarchies and city-states. The system of power of the French monarchy that was built in his view on the search for consensus between kings, aristocrats and the representatives of the third estate helped achieved stability and helped attain diplomatic and military victories. It is was a book written to teach a lesson to Venice for its attempts at intrigue in 1508—1513. To assess the role of Claude de Seyssel one needs to hold him as probably the first representative of the “mos gallicus”, the practice whereby scholars of humanism in France came to unite in themselves the status of a statesman, a jurist and a historian. It is likely that he was the person who not only introduced key sources on the history of Ancient polis, but also managed to provide, by way of pointers in his works to the concepts exhibited in Thucydides, the model of discussing in the new, humanistic context the successful and failed states and governments.