This essay aims to solve some problems concerning the Platonic principle holding that the government of the city has to be entrusted to the philosophers. The objects of their knowledge are transcendent (i.e. the forms), and therefore it is not fit for the practical sphere, that the philosophers have to rule. According to the author, a possible solution of this aporia can be found in the Statesman, where the Strange of Elea develops a particular form of measurement technique, based on the principles of convenience (prepon) and opportunity (kairos). Therefore the empirical expertise of the philosophers seems to be connected with the particular situation. In the last part of the essay the author tries to set the nature of the wisdom that allows the philosophers to apply their transcendent knowledge to the human world: it is a set of anthropological skills connected with the tripartition of the soul and the origin of the state.