The conduct of men and things? It must be exercised since the 19th century in Europe by mobilising ‘specialised knowledge’. Not by strict observance of the law, if not natural, or in the shade of Philoophia, but guided by ‘experience’. It is by no means a question of removing the most legitimate forms of government or of determining which part of human freedom may have received nature. Leaving these “metaphysical speculation”, government sciences have taken the way to a different narrative. If the management of men and territories should be removed from philosophical or legal categories, for example from the ancient Prudentia civic with his solemn precepts influenced by neo-stoicism, this is because the rationality of the government is now conceived as a rationality on the government. Because it is based on tools and techniques that are high as guarantors, if not on public policy criteria. This is the focus of this book from a colloquium organised by Cerat, in particular the Group of Historical Sociology of Government Sciences.